postgresql+ C#+ DHTMLX 学习汇总

前台: dhtmlxgrid.显示数据

　　  其格式为:

 {
　　rows:[
　　　　   {id:1,data:[1,2,3]}
         ,{}
         ]
}

如果在postgesql里直接生成这样的串呢??

这是就今天要做的事.

也是测试了一天,还是别人的帮助下完成:

1,2  本人自己写的,怎么也达不成这个目标:

3,    群友给的方案:完美解决

--方案1:
select json_agg(row_to_json(t))::text from (select id,concat_ws(',',pt_name,pt_description) as mydata from project_template )as t;
--结果[{"id":1,"myData":"whq,admin"},{"id":2,"myData":"eathon,sys"}]
--不理想
--方案2:
select json_agg(row_to_json(t))::text from (select id,'['|| concat_ws(',',pt_name,pt_description) ||']' as mydata from project_template ) as t
--结果[{"id":1,"myData":["whq,admin"]},{"id":2,"myData":["eathon,sys"]}]
好像对了,可是仔细看:"myData":["eathon,sys"]
　　　　不对,应该是:"myData":["eathon","sys"]
--方案3:
select json_agg(row_to_json(t))::text from (select id,array[pt_name,pt_description] as mydata from project_template where 1=1  and id=1) as t
--结果:[{"id":1,"myData":["whq","admin"]},{"id":2,"myData":["eathon","sys"]}]
 
--但是,大家注意了哟: 里面的数值是不带引号的,如果 用 JQUERY 的  $.getJSON()接受的话.里面的JSON 串  KEY,VALUE 都必须是双引号,否则不接受!
--见另一篇文章

$.getJSON(url,function success(){})回调函数不起作用

 --那么问题来了:  

--问题1:如果想返回所有的 KEY VALUE都带双引号该怎么办?

--

select json_agg(row_to_json(t))::text from (select id::text,array[pt_name,pt_description] as mydata from project_template where 1=1  and id=1) as t

--问题2: 如果查询的字段是个'col1,col2,col3'这样的变量应该怎么办?

--

select array_to_string(string_to_array('col1,col2,col3',','),'::text,')  --结果: col1::text,col2::text,col3

--快了,快要接近了:最后还少一个  ::text,因为要把所有的字段都给字符串化

--

select array_to_string(string_to_array('col1,col2,col3',','),'::text,')||'::text'   --结果:col1::text,col2::text,col3::text

--这样才算完美解决!

--这里再次感谢  pumpkin 群友!(没有你的指点,我不知道要走多少弯路!)

--也放一个自己'研究'了N久的一个查询存储过程

--其可以完美解决 生成 标准的JSON(都带双引号)

create or replace function f_query_all_json(
    table_name          text,         --表名
    query_feilds        text,        --需要查询的字段和字段值 'col1,col2,col3.......'
    condition_feilds    text,        --条件字段和字段值  "[{\"feild_name\":\"id\",\"feild_value\":1}]" 当然,这里应该可以简化一下
    out return_value    text         --返回值
) as $$
declare
    ex_sql             text;
    recs               record;
    _key               text ;
    _value             text;
    _result            text;
    _counts            integer;
begin
    --这里有个问题.就是query_feilds 里面字段如果不是TEXT 类型,得加上强制转换::text
    select array_to_string(string_to_array($2,','),'::text,')||'::text' into _key;
    ex_sql:='select json_agg(row_to_json(t))::text from (select id::text,array['||_key||'] as data from '
            ||quote_ident(table_name)
            || ' where 1=1 ';
    --设置条件参数
    for recs in select * from  json_array_elements(condition_feilds::json)  loop
        _key   := recs.value ->> 'feild_name';
        _value := recs.value ->> 'feild_value' ;
 
        if json_typeof(recs.value -> 'feild_value') ='number' then
            ex_sql:=ex_sql|| ' and ' || _key || '=' ||  _value;
        else
            ex_sql:=ex_sql|| ' and ' || _key || ' like '''||  (recs.value ->> 'feild_value') || '%''';
        end if;
    end loop;
    ex_sql:=ex_sql||') as t';
    execute ex_sql into _value;
    _result:='{"rows":'|| _value||'}';
    return_value := _result;
    -- return_value :=ex_sql;
end;
$$ language plpgsql;

 

 

一个 很牛老外写的SQL语句

CREATE TABLE customer_area_node
(
  id          bigserial NOT NULL PRIMARY KEY,
  customer_id integer   NOT NULL,
  parent_id   bigint,
  name        text,
  description text
);
 
INSERT INTO customer_area_node(customer_id, parent_id, name, description) VALUES
  (1,  NULL, 'name1',  ''),
  (2,  1,    'name2',  '1.2'),
  (3,  1,    'name3',  '1.3'),
  (4,  2,    'name4',  '1.2.4'),
  (5,  2,    'name5',  '1.2.5'),
  (6,  3,    'name6',  '1.3.6'),
  (7,  3,    'name7',  '1.3.7'),
  (8,  5,    'name8',  '1.2.5.8'),
  (9,  6,    'name9',  '1.3.6.9'),
  (10, 3,    'name10', '1.3.10'),
  (11, 9,    'name11', '1.3.6.9.11'),
  (12, 11,    'name12', '1.3.6.9.11.12');
 
WITH RECURSIVE c AS (
    SELECT *, 0 as lvl
    FROM   customer_area_node
    WHERE  customer_id = 1 AND parent_id IS NULL
    UNION ALL
    SELECT customer_area_node.*, c.lvl + 1
    FROM   customer_area_node
    JOIN   c ON customer_area_node.parent_id = c.id
),
maxlvl AS (
  SELECT max(lvl) maxlvl FROM c
),
j AS (
    SELECT c.*, json '[]' children
    FROM   c, maxlvl
    WHERE  lvl = maxlvl
  UNION ALL
    SELECT   (c).*, array_to_json(array_agg(j) || array(SELECT r
                                                        FROM   (SELECT l.*, json '[]' children
                                                                FROM   c l, maxlvl
                                                                WHERE  l.parent_id = (c).id
                                                                AND    l.lvl < maxlvl
                                                                AND    NOT EXISTS (SELECT 1
                                                                                   FROM   c lp
                                                                                   WHERE  lp.parent_id = l.id)) r)) children
    FROM     (SELECT c, j
              FROM   c
              JOIN   j ON j.parent_id = c.id) v
    GROUP BY v.c
)
SELECT row_to_json(j) json_tree
FROM   j
WHERE  lvl = 0;