SQL干货 增删改查（CURD）从入门到熟练 实用 - lbx

一、基本操作

1、添加（insert）

INSERT INTO user_temp (uid, username) VALUES (19088, 'asdf');

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2、修改（update）

UPDATE user_temp SET username = '111' WHERE uid = 19088;

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3、删除（delete）

DELETE FROM user_temp whe uid = 19088;

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4、查询（select）

SELECT id,username,spreader_uid,addtime FROM rrl_user WHERE addtime >= '2018/08/26';

二、SQL进阶

1、批量添加，INSERT INTO SELECT语句与SELECT INTO FROM语句区别

（1）INSERT INTO SELECT

Insert into Table2(field1,field2) select value1,value2 from Table1;

注：1.要求目标表Table2必须存在，并且字段field1,field2 也必须存在
2.如果Table2有主键而且不为空，则 field1，field2中必须包括主键

（2）SELECT INTO FROM

SELECT vale1, value2 into Table2 from Table1

注：1.要求目标表Table2不存在，因为在插入时会自动创建表Table2，并将Table1中指定字段数据复制到Table2中

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2、批量修改，根据一张表的数据批量修改另一张表的数据

UPDATE
    rrl_goods
SET
    beans_pay_rate = beans,
    cash_pay_rate = cash
FROM rrl_goods, test_goods_20180705
WHERE test_goods_20180705.goods_id = rrl_goods.id

注：beans_pay_rate 和 cash_pay_rate 是表 rrl_goods 的字段，beans 和 cash 是表 test_goods_20180705 的字段

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3、批量删除

（1）子查询删除

--删除所有满足子查询的数据
DELETE FROM user_temp whe uid IN (SELECT id FROM rrl_user WHERE addtime >= '2018/08/26');

（2）删除重复记录

delete from tablename where id not in (select max(id) from tablename group by col1,col2,...);

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4、查询进阶

（1）子查询方式1（IN或者=）

SELECT
    *
FROM
    rrl_user_money_record 
WHERE uid IN (
    SELECT id 
    FROM rrl_user 
    WHERE 
    addtime >= '2018/08/26'
);

（2）子查询方式2

SELECT
    *,
    (SELECT username FROM rrl_user WHERE id = uid) as username
FROM
    rrl_user_money_record 
WHERE uid = 19088;

（3）连接查询-左连接

SELECT
    r.*,u.username,u.addtime
FROM
    rrl_user_money_record r
LEFT JOIN rrl_user u
ON r.uid = u.id
WHERE u.addtime >= '2018/08/26';

左连接以左表数据为基准。

（4）连接查询-右连接

SELECT
    r.*,u.username,u.addtime
FROM
    rrl_user_money_record r
RIGHT JOIN rrl_user u
ON r.uid = u.id
WHERE u.addtime >= '2018/08/26';

右连接以右表数据为基准。

（5）连接查询-全连接

SELECT
    r.*,u.username,u.addtime
FROM
    rrl_user_money_record r
JOIN rrl_user u
ON r.uid = u.id
WHERE u.addtime >= '2018/08/26';

全连接以两表数据为基准。

（6）偏移分页查询（OFFSET-FETCH）

SELECT
    *
FROM
    rrl_user
ORDER BY
    addtime DESC
OFFSET 0 ROWS FETCH NEXT 10 ROWS ONLY;

注：偏移0行去10行，即显示第一页，每页10条数据。

SELECT
    *
FROM
    rrl_user
ORDER BY
    addtime DESC
OFFSET XXX ROWS FETCH NEXT {PageSize} ROWS ONLY;

注： XXX = (PageIndex - 1) * PageSize

（7）分组查询（可以去重）

SELECT
    uid,
    COUNT(1) c
FROM
    rrl_user_money_record 
WHERE addtime >= '2018/08/26'
GROUP BY uid
HAVING COUNT(1) > 1;

注： GROUP BY 后的字段必须在SELECT后面查询出来才行，分组查询也达到去重的目的。

（8）去重查询

SELECT
    DISTINCT uid
FROM
    rrl_user_money_record 
WHERE addtime >= '2018/08/26';

（9）随机取出10条数据查询

select top 10 * from rrl_user order by newid();