数据库的元数据抽取SQL

一、数据库驱动类、端口、默认用户名密码

数据库	驱动	端口	用户名	密码
MySQL	com.mysql.jdbc.Driver	3306	root	root
DB2	com.ibm.db2.jcc.DB2Driver	50000	db2inst1	db2inst1
Oracle	oracle.jdbc.OracleDriver	1521	system	manager
SQLServer	com.microsoft.sqlserver.jdbc.SQLServerDriver	1433	sa	sa
PostgreSQL	org.postgresql.Driver	5432	postgres	postgres
Mariadb	org.mariadb.jdbc.Driver	3306	root	root
GreenPlum	com.pivotal.jdbc.GreenplumDriver	5432	gpadmin	gpadmin
Teradata	com.teradata.jdbc.TeraDriver	1025	dbc	dbc

二、数据库的JDBC连接字符串

数据库	JDBC连接串
MySQL	jdbc:mysql://${dbHost}:${dbPort}/${dbName}?useSSL=false&useUnicode=true&characterEncoding=utf8
DB2	jdbc:db2://${dbHost}:${dbPort}/${dbName}
Oracle	jdbc:oracle:thin:@${dbHost}:${dbPort}:${dbName}       # SID jdbc:oracle:thin:@//${dbHost}:${dbPort}/${dbName}     # ServiceName
SQLServer	jdbc:sqlserver://${dbHost}:${dbPort};databaseName=${dbName}
PostgreSQL	jdbc:postgresql://${dbHost}:${dbPort}/${dbName}
Mariadb	jdbc:mariadb://${dbHost}:${dbPort}/${dbName}
GreenPlum	jdbc:pivotal:greenplum://${dbHost}:${dbPort};DatabaseName=${dbName}
Teradata	jdbc:teradata://${dbHost}/DATABASE=${dbName},DBS_PORT=${dbPort},CLIENT_CHARSET=EUC_CN,TMODE=TERA,CHARSET=ASCII

三、数据库的元数据抽取

• MySQL

      /* 完成 */
      SELECT UPPER(TRIM(T.TABLE_SCHEMA))                                      AS 模式
           , UPPER(TRIM(T.TABLE_NAME))                                        AS 表名称
           , T.TABLE_COMMENT                                                  AS 表注释
           , UPPER(TRIM(C.COLUMN_NAME))                                       AS 列名称
           , C.COLUMN_COMMENT                                                 AS 列注释
           , UPPER(TRIM(C.DATA_TYPE))                                         AS 列类型
           , IFNULL(C.CHARACTER_MAXIMUM_LENGTH,C.NUMERIC_PRECISION)           AS 列长度
           , C.NUMERIC_SCALE                                                  AS 小数位数
           , CASE WHEN C.COLUMN_KEY = 'PRI' THEN 'Y' ELSE NULL END            AS 是否主键
           , CASE WHEN C.IS_NULLABLE = 'NO' THEN 'N' ELSE NULL END            AS 是否可为空
           , C.COLUMN_DEFAULT                                                 AS 列默认值
           , I.INDEXES                                                        AS 索引名称
           , C.ORDINAL_POSITION                                               AS 列顺序
        FROM INFORMATION_SCHEMA.COLUMNS          C -- 列
  INNER JOIN INFORMATION_SCHEMA.TABLES           T -- 表
          ON T.TABLE_NAME   = C.TABLE_NAME
         AND T.TABLE_SCHEMA = C.TABLE_SCHEMA
         AND T.TABLE_TYPE   = 'BASE TABLE' -- 限制为表
   LEFT JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE K -- 列约束
          ON C.TABLE_NAME   = K.TABLE_NAME
         AND C.COLUMN_NAME  = K.COLUMN_NAME
         AND C.TABLE_SCHEMA = K.TABLE_SCHEMA
   LEFT JOIN (  -- 查询列上的索引名称(多个逗号分隔)
                SELECT TABLE_NAME, COLUMN_NAME, GROUP_CONCAT(INDEX_NAME) AS INDEXES
                  FROM INFORMATION_SCHEMA.STATISTICS
                 WHERE UPPER(TABLE_SCHEMA) = UPPER('${dbName}')
                 GROUP BY TABLE_NAME, COLUMN_NAME
             ) I
           ON C.TABLE_NAME  = I.TABLE_NAME
          AND C.COLUMN_NAME = I.COLUMN_NAME
       WHERE UPPER(TRIM(C.TABLE_SCHEMA)) = UPPER('${dbName}')
       ORDER BY C.TABLE_NAME, C.ORDINAL_POSITION
   

• DB2

     /* 完成
      * SYSIBM 基本表,对DB2使用进行最优化
      * SYSCAT 基于SYSIBM表的视图,对平常轻负荷使用进行优化
      */
      SELECT TRIM(C.TABSCHEMA)                         AS 模式
           , T.TABNAME                                 AS 表名称
           , T.REMARKS                                 AS 表注释
           , C.COLNAME                                 AS 列名称
           , C.REMARKS                                 AS 列注释
           , C.TYPENAME                                AS 列类型
           , C.LENGTH                                  AS 列长度
           , C.SCALE                                   AS 小数位数
           , NVL2(P.COLNAME,'Y',NULL)                  AS 主键
           , DECODE(C.NULLS,'N','N',NULL)              AS 可空
           , VARCHAR(C.DEFAULT)                        AS 默认
           , Y.INDEXES                                 AS 索引
           , C.COLNO                                   AS 列顺序
        FROM SYSCAT.COLUMNS C -- 列
  INNER JOIN SYSCAT.TABLES  T -- 表
          ON C.TABSCHEMA = T.TABSCHEMA
         AND C.TABNAME   = T.TABNAME
   LEFT JOIN ( -- DbVisualizer的DEBUG中取得
               SELECT TC.CONSTNAME, KC.COLNAME,TC.TABSCHEMA,TC.TABNAME
                 FROM SYSCAT.TABCONST  TC  -- 表约束: 主键P, 外键F, 唯一U, 表检查K
                    , SYSCAT.KEYCOLUSE KC  -- 关键列使用表
                WHERE TC.TABSCHEMA = KC.TABSCHEMA
                  AND TC.TABNAME   = KC.TABNAME
                  AND TC.CONSTNAME = KC.CONSTNAME
                  AND TC.TYPE      = 'P' -- 限制为主键
               ) P
          ON C.TABSCHEMA = P.TABSCHEMA
         AND C.TABNAME   = P.TABNAME
         AND C.COLNAME   = P.COLNAME
   LEFT JOIN ( -- 列及列上的多个索引
              SELECT X.TABSCHEMA, X.TABNAME, X.COLNAME, LISTAGG(X.INDNAME, ',') WITHIN GROUP(ORDER BY COLSORT) AS INDEXES
                FROM (-- 索引与列的对应关系
                      SELECT C.TABSCHEMA, C.TABNAME, C.COLNAME, I.INDNAME, INSTR(I.COLNAMES, '+' || C.COLNAME) AS COLSORT
                        FROM SYSCAT.INDEXES I -- 索引
                  INNER JOIN SYSCAT.COLUMNS C -- 列
                          ON C.TABSCHEMA = I.TABSCHEMA
                         AND C.TABNAME   = I.TABNAME
                         AND INSTR(I.COLNAMES, '+' || C.COLNAME) > 0 -- DB2索引对应的列放在COLNAMES里面,格式: +列1+列2
                       WHERE I.OWNERTYPE = 'U'
                     ) X
                GROUP BY X.TABSCHEMA, X.TABNAME, X.COLNAME
             ) Y
          ON C.TABSCHEMA = Y.TABSCHEMA
         AND C.TABNAME   = Y.TABNAME
         AND C.COLNAME   = Y.COLNAME
       WHERE T.TYPE      = 'T'
         AND T.OWNERTYPE = 'U'
         AND C.TABSCHEMA NOT LIKE 'SYS%'
         AND C.TABSCHEMA <> 'SQLJ'
       ORDER BY C.TABSCHEMA, C.TABNAME, C.COLNO

• Oracle

       /* 完成 */
        SELECT
               SYS_CONTEXT('USERENV','CURRENT_SCHEMA')              AS 模式
             , H.TABLE_NAME                                         AS 表名称
             , H.COMMENTS                                           AS 表注释
             , T.COLUMN_NAME                                        AS 列名称
             , A.COMMENTS                                           AS 列注释
             , T.DATA_TYPE                                          AS 列类型
             , NVL(T.DATA_LENGTH, T.DATA_PRECISION)                 AS 列长度
             , T.DATA_SCALE                                         AS 小数位数
             , B.PK                                                 AS 主键
             , DECODE(T.NULLABLE, 'N', 'N')                         AS 可空
             , T.DATA_DEFAULT                                       AS 默认
             , C.INDEXES                                            AS 索引
             , T.COLUMN_ID                                          AS 列顺序
          FROM USER_TAB_COLUMNS  T  -- 表列
     LEFT JOIN USER_TAB_COMMENTS H  -- 表注释
            ON H.TABLE_NAME = T.TABLE_NAME
     LEFT JOIN USER_COL_COMMENTS A  -- 列注释
            ON A.TABLE_NAME  = T.TABLE_NAME
           AND A.COLUMN_NAME = T.COLUMN_NAME
     LEFT JOIN (
                SELECT M.TABLE_NAME,M.COLUMN_NAME, 'Y' AS PK
                  FROM USER_CONS_COLUMNS M  -- 约束对应列
            INNER JOIN USER_CONSTRAINTS  N  -- 约束
                    ON M.CONSTRAINT_NAME = N.CONSTRAINT_NAME
                 WHERE N.CONSTRAINT_TYPE = 'P'
               ) B
            ON B.TABLE_NAME  = T.TABLE_NAME
           AND B.COLUMN_NAME = T.COLUMN_NAME
     LEFT JOIN (
                SELECT TABLE_NAME, COLUMN_NAME, LISTAGG(INDEX_NAME, ',') WITHIN GROUP(ORDER BY INDEX_NAME) AS INDEXES
                  FROM USER_IND_COLUMNS
                 GROUP BY TABLE_NAME, COLUMN_NAME
                ) C
            ON C.TABLE_NAME  = T.TABLE_NAME
           AND C.COLUMN_NAME = T.COLUMN_NAME
         WHERE T.TABLE_NAME IN (SELECT TABLE_NAME FROM USER_TABLES)
         ORDER BY T.TABLE_NAME, T.COLUMN_ID

• SQLServer

    /* 完成 */
    SELECT Upper(C.TABLE_SCHEMA)                                                AS 模式
         , Upper(C.TABLE_NAME)                                                  AS 表名称
         , M.TABCOMMENT                                                         AS 表注释
         , Upper(C.COLUMN_NAME)                                                 AS 列名称
         , M.COLCOMMENT                                                         AS 列注释
         , Upper(C.DATA_TYPE)                                                   AS 数据类型
         , ISNULL(C.CHARACTER_MAXIMUM_LENGTH,C.NUMERIC_PRECISION)               AS 列长度
         , C.NUMERIC_PRECISION                                                  AS 小数位数
         , CASE WHEN P.COLUMN_NAME IS NULL THEN NULL ELSE 'Y' END               AS 是否主键
         , CASE WHEN SUBSTRING(C.IS_NULLABLE,1,1) = 'N' THEN 'N' ELSE NULL END  AS 是否可为空
         , C.COLUMN_DEFAULT                                                     AS 列默认值
         , N.INDEXES                                                            AS 索引名称
         , C.ORDINAL_POSITION                                                   AS 列顺序
      FROM INFORMATION_SCHEMA.COLUMNS C
 LEFT JOIN (  -- 表和列的注释
                SELECT  T.NAME                            AS TABNAME
                      , CONVERT(VARCHAR(1024),E1.VALUE)   AS TABCOMMENT
                      , C.NAME                            AS COLNAME
                      , CONVERT(VARCHAR(1024),E2.VALUE)   AS COLCOMMENT
                   FROM SYS.TABLES  T  -- 表
             INNER JOIN SYS.COLUMNS C  -- 列
                     ON C.OBJECT_ID = T.OBJECT_ID
              LEFT JOIN SYS.EXTENDED_PROPERTIES E1 -- 系统属性表
                     ON E1.MAJOR_ID = T.OBJECT_ID
                    AND E1.CLASS    = 1
                    AND E1.MINOR_ID = 0            -- 限制是表的注释
              LEFT JOIN SYS.EXTENDED_PROPERTIES E2 -- 系统属性表
                     ON E2.MAJOR_ID = C.OBJECT_ID
                    AND E2.CLASS    = 1
                    AND E2.MINOR_ID = C.COLUMN_ID  -- 限制是列的注释
                  WHERE ObjectProperty(T.OBJECT_ID, 'IsUserTable') = 1 -- 限制为用户建立的表
           ) M
        ON M.TABNAME = C.TABLE_NAME
       AND M.COLNAME = C.COLUMN_NAME
 LEFT JOIN ( -- 主键约束
             SELECT TC.TABLE_SCHEMA, TC.TABLE_NAME, CC.COLUMN_NAME
              FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS        TC  -- 表约束(表名,约束名,约束类型)
        INNER JOIN INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE  CC  -- 约束使用的列(根据约束名关联)
                ON TC.CONSTRAINT_NAME = CC.CONSTRAINT_NAME
             WHERE TC.CONSTRAINT_TYPE = 'PRIMARY KEY'
            ) P
        ON C.TABLE_SCHEMA = P.TABLE_SCHEMA
       AND C.TABLE_NAME   = P.TABLE_NAME
       AND C.COLUMN_NAME  = P.COLUMN_NAME
 LEFT JOIN ( -- 索引
            SELECT TABLE_SCHEMA, TABLE_NAME, COLUMN_NAME, LEFT(INDEXES, LEN(INDEXES) - 1) AS INDEXES
             FROM (
                    SELECT K.TABLE_SCHEMA
                         , K.TABLE_NAME
                         , K.COLUMN_NAME
                         , (SELECT N.CONSTRAINT_NAME + ','
                              FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE N
                             WHERE N.TABLE_SCHEMA = K.TABLE_SCHEMA
                               AND N.TABLE_NAME   = K.TABLE_NAME
                               AND N.COLUMN_NAME  = K.COLUMN_NAME
                               FOR XML PATH('')) AS INDEXES
                      FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE K
                      GROUP BY K.TABLE_SCHEMA, K.TABLE_NAME, K.COLUMN_NAME
                  ) K
           ) N
        ON C.TABLE_SCHEMA = N.TABLE_SCHEMA
       AND C.TABLE_NAME   = N.TABLE_NAME
       AND C.COLUMN_NAME  = N.COLUMN_NAME
     ORDER BY C.TABLE_SCHEMA, C.TABLE_NAME, C.ORDINAL_POSITION
     

• PostgreSQL

            /* 除了索引, 其他完成 */
            SELECT
                   UPPER(C.TABLE_SCHEMA)                                            AS 模式
                 , UPPER(C.TABLE_NAME)                                              AS 表名称
                 , C.TAB_COMMENT                                                    AS 表注释
                 , UPPER(C.COLUMN_NAME)                                             AS 列名称
                 , C.COL_COMMENT                                                    AS 列注释
                 , UPPER(C.DATA_TYPE)                                               AS 列类型
                 , COALESCE(C.CHARACTER_MAXIMUM_LENGTH,C.NUMERIC_PRECISION)         AS 列长度
                 , C.NUMERIC_SCALE                                                  AS 小数位数
                 , C.COL_PRIMARY                                                    AS 是否主键
                 , CASE WHEN SUBSTR(C.IS_NULLABLE,1,1) = 'N' THEN 'N'ELSE NULL END  AS 是否可空
                 , CASE -- 字符串的默认值存储的是: 'N'::CHARACTER VARYING, 因此特殊处理
                        WHEN SUBSTR(C.COLUMN_DEFAULT,1,1) = ''''
                        THEN SUBSTR(C.COLUMN_DEFAULT,2, POSITION('''' IN SUBSTR(C.COLUMN_DEFAULT,2)) - 1)
                        ELSE C.COLUMN_DEFAULT
                   END                                                              AS 默认
                 , NULL                                                             AS 索引     -- PostgreSQL中的索引好麻烦,没找到合适的方法取
                 , C.ORDINAL_POSITION                                               AS 字段顺序
              FROM (
                -- information_schema.columns 的定义: 追加表注释,列注释及索引信息
                SELECT current_database()::information_schema.sql_identifier AS table_catalog, nc.nspname::information_schema.sql_identifier AS table_schema, c.relname::information_schema.sql_identifier AS table_name, a.attname::information_schema.sql_identifier AS column_name, a.attnum::information_schema.cardinal_number AS ordinal_position, pg_get_expr(ad.adbin, ad.adrelid)::information_schema.character_data AS column_default,
                        CASE
                            WHEN a.attnotnull OR (t.typtype = 'd'::"char" AND t.typnotnull) THEN 'NO'::text
                            ELSE 'YES'::text
                        END::information_schema.character_data AS is_nullable,
                        CASE
                            WHEN t.typtype = 'd'::"char" THEN
                            CASE
                                WHEN bt.typelem <> 0::oid AND bt.typlen = (-1) THEN 'ARRAY'::text
                                WHEN nbt.nspname = 'pg_catalog'::name THEN format_type(t.typbasetype, NULL::integer)
                                ELSE 'USER-DEFINED'::text
                            END
                            ELSE
                            CASE
                                WHEN t.typelem <> 0::oid AND t.typlen = (-1) THEN 'ARRAY'::text
                                WHEN nt.nspname = 'pg_catalog'::name THEN format_type(a.atttypid, NULL::integer)
                                ELSE 'USER-DEFINED'::text
                            END
                        END::information_schema.character_data AS data_type, information_schema._pg_char_max_length(information_schema._pg_truetypid(a.*, t.*), information_schema._pg_truetypmod(a.*, t.*))::information_schema.cardinal_number AS character_maximum_length, information_schema._pg_char_octet_length(information_schema._pg_truetypid(a.*, t.*), information_schema._pg_truetypmod(a.*, t.*))::information_schema.cardinal_number AS character_octet_length, information_schema._pg_numeric_precision(information_schema._pg_truetypid(a.*, t.*), information_schema._pg_truetypmod(a.*, t.*))::information_schema.cardinal_number AS numeric_precision, information_schema._pg_numeric_precision_radix(information_schema._pg_truetypid(a.*, t.*), information_schema._pg_truetypmod(a.*, t.*))::information_schema.cardinal_number AS numeric_precision_radix, information_schema._pg_numeric_scale(information_schema._pg_truetypid(a.*, t.*), information_schema._pg_truetypmod(a.*, t.*))::information_schema.cardinal_number AS numeric_scale, information_schema._pg_datetime_precision(information_schema._pg_truetypid(a.*, t.*), information_schema._pg_truetypmod(a.*, t.*))::information_schema.cardinal_number AS datetime_precision, NULL::character varying::information_schema.character_data AS interval_type, NULL::character varying::information_schema.character_data AS interval_precision, NULL::character varying::information_schema.sql_identifier AS character_set_catalog, NULL::character varying::information_schema.sql_identifier AS character_set_schema, NULL::character varying::information_schema.sql_identifier AS character_set_name, NULL::character varying::information_schema.sql_identifier AS collation_catalog, NULL::character varying::information_schema.sql_identifier AS collation_schema, NULL::character varying::information_schema.sql_identifier AS collation_name,
                        CASE
                            WHEN t.typtype = 'd'::"char" THEN current_database()
                            ELSE NULL::name
                        END::information_schema.sql_identifier AS domain_catalog,
                        CASE
                            WHEN t.typtype = 'd'::"char" THEN nt.nspname
                            ELSE NULL::name
                        END::information_schema.sql_identifier AS domain_schema,
                        CASE
                            WHEN t.typtype = 'd'::"char" THEN t.typname
                            ELSE NULL::name
                        END::information_schema.sql_identifier AS domain_name, current_database()::information_schema.sql_identifier AS udt_catalog, COALESCE(nbt.nspname, nt.nspname)::information_schema.sql_identifier AS udt_schema, COALESCE(bt.typname, t.typname)::information_schema.sql_identifier AS udt_name, NULL::character varying::information_schema.sql_identifier AS scope_catalog, NULL::character varying::information_schema.sql_identifier AS scope_schema, NULL::character varying::information_schema.sql_identifier AS scope_name, NULL::integer::information_schema.cardinal_number AS maximum_cardinality, a.attnum::information_schema.sql_identifier AS dtd_identifier, 'NO'::character varying::information_schema.character_data AS is_self_referencing, 'NO'::character varying::information_schema.character_data AS is_identity, NULL::character varying::information_schema.character_data AS identity_generation, NULL::character varying::information_schema.character_data AS identity_start, NULL::character varying::information_schema.character_data AS identity_increment, NULL::character varying::information_schema.character_data AS identity_maximum, NULL::character varying::information_schema.character_data AS identity_minimum, NULL::character varying::information_schema.character_data AS identity_cycle, 'NEVER'::character varying::information_schema.character_data AS is_generated, NULL::character varying::information_schema.character_data AS generation_expression,
                        CASE
                            WHEN c.relkind = 'r'::"char" THEN 'YES'::text
                            ELSE 'NO'::text
                        END::information_schema.character_data AS is_updatable
                       -- 追加两个注释和是否为主键
                       , cast(obj_description(c.relfilenode,'pg_class') as varchar) AS tab_comment
                       , col_description(a.attrelid,a.attnum)                       AS col_comment
                       , case when con.conname is not null then 'Y' else null end   as col_primary
                   FROM pg_attribute a
                   -- 追加是不是主键
                   LEFT JOIN pg_constraint con ON con.conrelid  =  a.attrelid AND con.conkey[] =  a.attnum
                   LEFT JOIN pg_attrdef ad ON a.attrelid = ad.adrelid AND a.attnum = ad.adnum, pg_class c, pg_namespace nc, pg_type t
                   JOIN pg_namespace nt ON t.typnamespace = nt.oid
                   LEFT JOIN (pg_type bt
                   JOIN pg_namespace nbt ON bt.typnamespace = nbt.oid) ON t.typtype = 'd'::"char" AND t.typbasetype = bt.oid
 
                   WHERE a.attrelid = c.oid AND a.atttypid = t.oid AND nc.oid = c.relnamespace AND NOT pg_is_other_temp_schema(nc.oid) AND a.attnum > 0 AND NOT a.attisdropped AND (c.relkind = ANY (ARRAY['r'::"char", 'v'::"char"])) AND (pg_has_role(c.relowner, 'USAGE'::text) OR has_table_privilege(c.oid, 'SELECT'::text) OR has_table_privilege(c.oid, 'INSERT'::text) OR has_table_privilege(c.oid, 'UPDATE'::text) OR has_table_privilege(c.oid, 'REFERENCES'::text))
              ) c
              WHERE C.TABLE_NAME IN (SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_TYPE = 'BASE TABLE')
                AND C.TABLE_SCHEMA NOT IN ('information_schema','pg_catalog') -- 排除信息模式和系统本身元数据模式
                AND C.TABLE_SCHEMA NOT LIKE 'pg|_%' escape '|' -- 排除pg系统表
                AND C.TABLE_SCHEMA NOT LIKE 'gp|_%' escape '|' -- 排除gp系统表
              ORDER BY C.TABLE_CATALOG, C.TABLE_SCHEMA, C.TABLE_NAME, C.ORDINAL_POSITION

• Mariadb(参考MySQL)
• GreenPlum

            /* 除了索引和分布键, 其他完成 */
            SELECT
                   UPPER(C.TABLE_SCHEMA)                                            AS 模式
                 , UPPER(C.TABLE_NAME)                                              AS 表名称
                 , C.TAB_COMMENT                                                    AS 表注释
                 , UPPER(C.COLUMN_NAME)                                             AS 列名称
                 , C.COL_COMMENT                                                    AS 列注释
                 , UPPER(C.DATA_TYPE)                                               AS 列类型
                 , COALESCE(C.CHARACTER_MAXIMUM_LENGTH,C.NUMERIC_PRECISION)         AS 列长度
                 , C.NUMERIC_SCALE                                                  AS 小数位数
                 , C.COL_PRIMARY                                                    AS 是否主键
                 , CASE WHEN SUBSTR(C.IS_NULLABLE,1,1) = 'N' THEN 'N'ELSE NULL END  AS 是否可空
                 , CASE -- 字符串的默认值存储的是: 'N'::CHARACTER VARYING, 因此特殊处理
                        WHEN SUBSTR(C.COLUMN_DEFAULT,1,1) = ''''
                        THEN SUBSTR(C.COLUMN_DEFAULT,2, POSITION('''' IN SUBSTR(C.COLUMN_DEFAULT,2)) - 1)
                        ELSE C.COLUMN_DEFAULT
                   END                                                              AS 默认
                 , NULL                                                             AS 索引     -- PostgreSQL中的索引好麻烦,没找到合适的方法取
                 , C.ORDINAL_POSITION                                               AS 字段顺序
              FROM (
                -- information_schema.columns 的定义: 追加表注释,列注释及索引信息
                SELECT current_database()::information_schema.sql_identifier AS table_catalog, nc.nspname::information_schema.sql_identifier AS table_schema, c.relname::information_schema.sql_identifier AS table_name, a.attname::information_schema.sql_identifier AS column_name, a.attnum::information_schema.cardinal_number AS ordinal_position, pg_get_expr(ad.adbin, ad.adrelid)::information_schema.character_data AS column_default,
                        CASE
                            WHEN a.attnotnull OR (t.typtype = 'd'::"char" AND t.typnotnull) THEN 'NO'::text
                            ELSE 'YES'::text
                        END::information_schema.character_data AS is_nullable,
                        CASE
                            WHEN t.typtype = 'd'::"char" THEN
                            CASE
                                WHEN bt.typelem <> 0::oid AND bt.typlen = (-1) THEN 'ARRAY'::text
                                WHEN nbt.nspname = 'pg_catalog'::name THEN format_type(t.typbasetype, NULL::integer)
                                ELSE 'USER-DEFINED'::text
                            END
                            ELSE
                            CASE
                                WHEN t.typelem <> 0::oid AND t.typlen = (-1) THEN 'ARRAY'::text
                                WHEN nt.nspname = 'pg_catalog'::name THEN format_type(a.atttypid, NULL::integer)
                                ELSE 'USER-DEFINED'::text
                            END
                        END::information_schema.character_data AS data_type, information_schema._pg_char_max_length(information_schema._pg_truetypid(a.*, t.*), information_schema._pg_truetypmod(a.*, t.*))::information_schema.cardinal_number AS character_maximum_length, information_schema._pg_char_octet_length(information_schema._pg_truetypid(a.*, t.*), information_schema._pg_truetypmod(a.*, t.*))::information_schema.cardinal_number AS character_octet_length, information_schema._pg_numeric_precision(information_schema._pg_truetypid(a.*, t.*), information_schema._pg_truetypmod(a.*, t.*))::information_schema.cardinal_number AS numeric_precision, information_schema._pg_numeric_precision_radix(information_schema._pg_truetypid(a.*, t.*), information_schema._pg_truetypmod(a.*, t.*))::information_schema.cardinal_number AS numeric_precision_radix, information_schema._pg_numeric_scale(information_schema._pg_truetypid(a.*, t.*), information_schema._pg_truetypmod(a.*, t.*))::information_schema.cardinal_number AS numeric_scale, information_schema._pg_datetime_precision(information_schema._pg_truetypid(a.*, t.*), information_schema._pg_truetypmod(a.*, t.*))::information_schema.cardinal_number AS datetime_precision, NULL::character varying::information_schema.character_data AS interval_type, NULL::character varying::information_schema.character_data AS interval_precision, NULL::character varying::information_schema.sql_identifier AS character_set_catalog, NULL::character varying::information_schema.sql_identifier AS character_set_schema, NULL::character varying::information_schema.sql_identifier AS character_set_name, NULL::character varying::information_schema.sql_identifier AS collation_catalog, NULL::character varying::information_schema.sql_identifier AS collation_schema, NULL::character varying::information_schema.sql_identifier AS collation_name,
                        CASE
                            WHEN t.typtype = 'd'::"char" THEN current_database()
                            ELSE NULL::name
                        END::information_schema.sql_identifier AS domain_catalog,
                        CASE
                            WHEN t.typtype = 'd'::"char" THEN nt.nspname
                            ELSE NULL::name
                        END::information_schema.sql_identifier AS domain_schema,
                        CASE
                            WHEN t.typtype = 'd'::"char" THEN t.typname
                            ELSE NULL::name
                        END::information_schema.sql_identifier AS domain_name, current_database()::information_schema.sql_identifier AS udt_catalog, COALESCE(nbt.nspname, nt.nspname)::information_schema.sql_identifier AS udt_schema, COALESCE(bt.typname, t.typname)::information_schema.sql_identifier AS udt_name, NULL::character varying::information_schema.sql_identifier AS scope_catalog, NULL::character varying::information_schema.sql_identifier AS scope_schema, NULL::character varying::information_schema.sql_identifier AS scope_name, NULL::integer::information_schema.cardinal_number AS maximum_cardinality, a.attnum::information_schema.sql_identifier AS dtd_identifier, 'NO'::character varying::information_schema.character_data AS is_self_referencing, 'NO'::character varying::information_schema.character_data AS is_identity, NULL::character varying::information_schema.character_data AS identity_generation, NULL::character varying::information_schema.character_data AS identity_start, NULL::character varying::information_schema.character_data AS identity_increment, NULL::character varying::information_schema.character_data AS identity_maximum, NULL::character varying::information_schema.character_data AS identity_minimum, NULL::character varying::information_schema.character_data AS identity_cycle, 'NEVER'::character varying::information_schema.character_data AS is_generated, NULL::character varying::information_schema.character_data AS generation_expression,
                        CASE
                            WHEN c.relkind = 'r'::"char" THEN 'YES'::text
                            ELSE 'NO'::text
                        END::information_schema.character_data AS is_updatable
                       -- 追加两个注释和是否为主键
                       , cast(obj_description(c.relfilenode,'pg_class') as varchar) AS tab_comment
                       , col_description(a.attrelid,a.attnum)                       AS col_comment
                       , case when con.conname is not null then 'Y' else null end   as col_primary
                   FROM pg_attribute a
                   -- 追加是不是主键
                   LEFT JOIN pg_constraint con ON con.conrelid  =  a.attrelid AND con.conkey[] =  a.attnum
                   LEFT JOIN pg_attrdef ad ON a.attrelid = ad.adrelid AND a.attnum = ad.adnum, pg_class c, pg_namespace nc, pg_type t
                   JOIN pg_namespace nt ON t.typnamespace = nt.oid
                   LEFT JOIN (pg_type bt
                   JOIN pg_namespace nbt ON bt.typnamespace = nbt.oid) ON t.typtype = 'd'::"char" AND t.typbasetype = bt.oid
 
                   WHERE a.attrelid = c.oid AND a.atttypid = t.oid AND nc.oid = c.relnamespace AND NOT pg_is_other_temp_schema(nc.oid) AND a.attnum > 0 AND NOT a.attisdropped AND (c.relkind = ANY (ARRAY['r'::"char", 'v'::"char"])) AND (pg_has_role(c.relowner, 'USAGE'::text) OR has_table_privilege(c.oid, 'SELECT'::text) OR has_table_privilege(c.oid, 'INSERT'::text) OR has_table_privilege(c.oid, 'UPDATE'::text) OR has_table_privilege(c.oid, 'REFERENCES'::text))
              ) c
              WHERE C.TABLE_NAME IN (SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_TYPE = 'BASE TABLE')
                AND C.TABLE_SCHEMA NOT IN ('information_schema','pg_catalog') -- 排除信息模式和系统本身元数据模式
                AND C.TABLE_SCHEMA NOT LIKE 'pg|_%' escape '|' -- 排除pg系统表
                AND C.TABLE_SCHEMA NOT LIKE 'gp|_%' escape '|' -- 排除gp系统表
              ORDER BY C.TABLE_CATALOG, C.TABLE_SCHEMA, C.TABLE_NAME, C.ORDINAL_POSITION

• Teradata

           /* 完成 */
           SELECT
                  TRIM(C.DatabaseName)                                         AS 数据库
                , TRIM(C.TableName)                                            AS 表名称
                , TRIM(T.CommentString)                                        AS 表注释
                , TRIM(C.ColumnName)                                           AS 列名称
                , TRIM(NVL(C.ColumnTitle,C.CommentString))                     AS 列注释
                /* Teradata® RDBMS Data Dictionary的P76页System View Columns Reference的ColumnType枚举 (B035-1092-061A)*/
                /* 版本较旧,枚举值可能不全, 最新版手册没有找到这个枚举值 */
                , CASE TRIM(C.ColumnType)
                    WHEN 'AT' THEN 'TIME'
                    WHEN 'BF' THEN 'BYTE'
                    WHEN 'BV' THEN 'VARBYTE'
                    WHEN 'CF' THEN 'CHAR'
                    WHEN 'CV' THEN 'VARCHAR'
                    WHEN 'D'  THEN 'DECIMAL'
                    WHEN 'DA' THEN 'DATE'
                    WHEN 'DH' THEN 'INTERVAL DAY TO HOUR'
                    WHEN 'DM' THEN 'INTERVAL DAY TO MINUTE'
                    WHEN 'DS' THEN 'INTERVAL DAY TO SECOND'
                    WHEN 'DY' THEN 'INTERVAL DAY'
                    WHEN 'F'  THEN 'FLOAT'
                    WHEN 'GF' THEN 'GRAPHIC'
                    WHEN 'GV' THEN 'VARGRAPHIC'
                    WHEN 'HM' THEN 'INTERVAL HOUR TO MINUTE'
                    WHEN 'HR' THEN 'INTERVAL HOUR'
                    WHEN 'HS' THEN 'INTERVAL HOUR TO SECOND'
                    WHEN 'I1' THEN 'BYTEINT'
                    WHEN 'I2' THEN 'SMALLINT'
                    WHEN 'I8' THEN 'BYTEINTEGER'
                    WHEN 'I'  THEN 'INTEGER'
                    WHEN 'MI' THEN 'INTERVAL MINUTE'
                    WHEN 'MO' THEN 'INTERVAL MONTH'
                    WHEN 'MS' THEN 'INTERVAL MINUTE TO SECOND'
                    WHEN 'SC' THEN 'INTERVAL SECOND'
                    WHEN 'SZ' THEN 'TIMESTAMP WITH TIME ZONE'
                    WHEN 'TS' THEN 'TIMESTAMP'
                    WHEN 'TZ' THEN 'TIME WITH TIME ZONE'
                    WHEN 'YM' THEN 'INTERVAL YEAR TO MONTH'
                    WHEN 'YR' THEN 'INTERVAL YEAR'
                    ELSE C.ColumnType
                  END
                , NVL(C.ColumnLength,C.DecimalTotalDigits)                     AS 数据长度
                , C.DecimalFractionalDigits                                    AS 小数位数
                , NVL2(I.ColumnName,'Y',NULL)                                  AS 是否主键
                , CASE WHEN C.Nullable = 'N' THEN 'N' ELSE NULL END            AS 是否可空
                , C.DefaultValue                                               AS 默认值
                , H.Indexes                                                    AS 索引名称
                , C.ColumnId                                                   AS 列顺序
            FROM DBC.COLUMNS  C  -- 列元数据
      INNER JOIN DBC.TABLES   T  -- 表元数据
              ON T.DatabaseName = C.DatabaseName
             AND T.TableName    = C.TableName
             AND T.TableKind    = 'T'
       LEFT JOIN DBC.INDICES  I  -- 索引
              ON I.DatabaseName = C.DatabaseName
             AND I.TableName    = C.TableName
             AND I.ColumnName   = C.ColumnName
             AND I.INDEXTYPE    = 'K' -- 限制为主键
       LEFT JOIN (
                   /* If Teradata's XML-services are installed (default since 14.10?) there's a function named XMLAGG */
                   SELECT DatabaseName, TableName, ColumnName
                        , TRIM(TRAILING ',' FROM (XMLAGG(TRIM(ColumnName)|| ',' ORDER BY ColumnPosition) (VARCHAR(10000)))) AS Indexes
                     FROM DBC.INDICES
                    WHERE IndexName IS NOT NULL
                    GROUP BY DatabaseName, TableName, ColumnName
                 ) H
              ON I.DatabaseName = H.DatabaseName
             AND I.TableName    = H.TableName
             AND I.ColumnName   = H.ColumnName
           ORDER BY C.DatabaseName, C.TableName, C.ColumnId