MySQL笔记（四）DDL与DML风格参考

便于 COPY

▲ 在所有操作之前：

SET character_set_database=utf8;

确保 ↓

mysql> SHOW VARIABLES LIKE "%char%";
+--------------------------+----------------------------+
| Variable_name | Value |
+--------------------------+----------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | utf8 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | latin1 |
| character_set_system | utf8 |
| character_sets_dir | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)

▲ 创建数据库：

CREATE DATABASE sql_lab;

▲ 然后创建表：

CREATE TABLE chucang (
    chucang_no VARCHAR(12),
    enterprise_name VARCHAR(20),
    chucang_time DATE,
    chucang_type CHAR(1) COMMENT '企业性质，Y 公有，N 私有',
    enterprise_address VARCHAR(50),
    delivery_car_no VARCHAR(12),
    chucang_sum DECIMAL(8,2),

    PRIMARY KEY(chucang_no)

)    ENGINE=INNODB DEFAULT CHARSET=utf8;

CREATE TABLE chucang_detail (
    chucang_no VARCHAR(12),
    product_no VARCHAR(12),
    price DECIMAL(8,2),
    quantity INT,
    total DECIMAL(8,2),

    FOREIGN KEY (chucang_no)
        REFERENCES chucang(chucang_no)

)    ENGINE=INNODB DEFAULT CHARSET=utf8;

PS. 别漏掉 DEFAULT CHARSET=utf8

▲ 确认表是否创建：

mysql> SHOW TABLES;
+-------------------+
| Tables_in_sql_lab |
+-------------------+
| chucang           |
| chucang_detail    |
+-------------------+
2 rows in set (0.01 sec)

▲ 插入数据：

INSERT INTO chucang
    (chucang_no,
    enterprise_name,
    chucang_time,
    chucang_type,
    enterprise_address,
    delivery_car_no,
    chucang_sum)
VALUES
    ('',
    'enterprise_a',
    '1997-10-11',
    'Y',
    '????',
    '',
    0.00),
    ('',
    'enterprise_b',
    '1997-10-21',
    'Y',
    'shanghai',
    '',
    0.00),
    ('',
    'enterprise_c',
    '1997-10-22',
    'N',
    'beijin',
    '',
    0.00),
    ('',
    'enterprise_d',
    '1997-10-23',
    'Y',
    'shanghai',
    '',
    0.00),
    ('',
    'enterprise_e',
    '1997-10-24',
    'N',
    'guangdong',
    '',
    0.00);

INSERT INTO chucang_detail
    (chucang_no,
    product_no,
    price,
    quantity,
    total)
VALUES
    ('',
    '',
    30.5,
    20,
    0.00),
    ('',
    '',
    31.5,
    22,
    0.00),
    ('',
    '',
    40.5,
    20,
    0.00),
    ('',
    '',
    41.5,
    20,
    0.00),
    ('',
    '',
    43.5,
    20,
    0.00);

▲ 检查数据：

SELECT *
FROM chucang_detail
LIMIT 3\G

▲ 修改表，插入一个新的字段/属性/列：

ALTER TABLE chucang
ADD enterprise_phone CHAR(20);

▲ 检查是否修改成功：

mysql> DESCRIBE chucang;

▲ 更新数据：

UPDATE chucang_detail
SET total = quantity * price;

UPDATE chucang x, chucang_detail y
SET x.chucang_sum = y.total
WHERE x.chucang_no = y.chucang_no;
-- 多表示例 ↑ ↓
UPDATE chucang x
SET x.chucang_sum = (
    SELECT SUM(total)
    FROM chucang_detail y
    GROUP BY y.chucang_no
    HAVING y.chucang_no = x.chucang_no
)

▲ 最简单的查询：

SELECT chucang_sum
FROM chucang
WHERE chucang_type = 'Y'

▲ 排序：

SELECT chucang_no, enterprise_name
FROM chucang
ORDER BY chucang_no

▲ 子查询：

SELECT chucang_no
FROM chucang_detail
WHERE chucang_no NOT IN (
    SELECT chucang_no
    FROM chucang
)

▲ 分组过滤 & 聚集函数：

SELECT chucang_type, SUM(chucang_sum)
FROM chucang
GROUP BY chucang_type
HAVING chucang_type = 'Y'

▲ 本题无关，联表查询示例：

SELECT employee_no, employee_name, product_name, quantity, price
FROM employee x
LEFT OUTER JOIN order_master y ON x.employee_no = y.saler_no
LEFT OUTER JOIN order_detail z ON z.order_no = y.order_no
LEFT OUTER JOIN product m ON m.product_no = z.product_no
WHERE (
    SELECT COUNT(DISTINCT product_no)
    FROM order_master w
    LEFT OUTER JOIN order_detail e ON w.order_no = e.order_no
    WHERE w.saler_no = x.employee_no) >= 5
ORDER BY employee_no