MySql中4種批量更新的方法
mysql 批量更新共有以下四種辦法
1、.replace into 批量更新
replace into test_tbl (id,dr) values (1,'2'),(2,'3'),...(x,'y');
例子:
replace into book (
'Id',
'Author',
'CreatedTime',
'UpdatedTime'
) values (
1,
'張飛',
'2016-12-12 12:20',
'2016-12-12 12:20'
),(
2,
'關羽',
'2016-12-12 12:20',
'2016-12-12 12:20');
2、insert into ...on duplicate key update批量更新
insert into test_tbl (id,dr) values (1,'2'),(2,'3'),...(x,'y') on duplicate key update dr=values(dr);
例子:
insert into book
(`Id`,`Author`,`CreatedTime`,`UpdatedTime`)
values
(1,'張飛2','2017-12-12 12:20','2017-12-12 12:20'),
(2,'關羽2','2017-12-12 12:20','2017-12-12 12:20')
on duplicate key update
Author=values(Author),
CreatedTime=values(CreatedTime),
UpdatedTime=values(UpdatedTime);
replace into 和 insert into on duplicate key update的不同在於:
- replace into 操作本質是對重複的記錄先delete 後insert,如果更新的字段不全會將缺失的字段置爲缺省值,用這個要悠着點否則不小心清空大量數據可不是鬧着玩的。
- insert into 則是隻update重複記錄,不會改變其它字段。
3.創建臨時表,先更新臨時表,然後從臨時表中update
create temporary table tmp(id int(4) primary key,dr varchar(50));
insert into tmp values (0,'gone'), (1,'xx'),...(m,'yy');
update test_tbl, tmp set test_tbl.dr=tmp.dr where test_tbl.id=tmp.id;
注意:這種方法需要用戶有temporary 表的create 權限。
4、使用mysql 自帶的語句構建批量更新
mysql 實現批量 可以用點小技巧來實現:
UPDATE yoiurtable
SET dingdan = CASE id
WHEN 1 THEN 3
WHEN 2 THEN 4
WHEN 3 THEN 5
END
WHERE id IN (1,2,3)
這句sql 的意思是,更新dingdan 字段,如果id=1 則dingdan 的值爲3,如果id=2 則dingdan 的值爲4……
where部分不影響代碼的執行,但是會提高sql執行的效率。確保sql語句僅執行需要修改的行數,這裏只有3條數據進行更新,而where子句確保只有3行數據執行。
例子:
UPDATE book
SET Author = CASE id
WHEN 1 THEN '黃飛鴻'
WHEN 2 THEN '方世玉'
WHEN 3 THEN '洪熙官'
END
WHERE id IN (1,2,3)
如果更新多個值的話,只需要稍加修改:
UPDATE categories
SET dingdan = CASE id
WHEN 1 THEN 3
WHEN 2 THEN 4
WHEN 3 THEN 5
END,
title = CASE id
WHEN 1 THEN 'New Title 1'
WHEN 2 THEN 'New Title 2'
WHEN 3 THEN 'New Title 3'
END
WHERE id IN (1,2,3)
例子:
UPDATE book
SET Author = CASE id
WHEN 1 THEN '黃飛鴻2'
WHEN 2 THEN '方世玉2'
WHEN 3 THEN '洪熙官2'
END,
Code = CASE id
WHEN 1 THEN 'HFH2'
WHEN 2 THEN 'FSY2'
WHEN 3 THEN 'HXG2'
END
WHERE id IN (1,2,3)
具體的MyBatis代碼如下:
<update id="update" parameterType="java.util.List">
UPDATE dic_col_display
SET column_code = CASE id
<foreach collection="list" item="item" index="index" open="" separator="" close="">
WHEN #{item.id} THEN #{item.column_code}
</foreach>
END,
column_desc = CASE id
<foreach collection="list" item="item" index="index" open="" separator="" close="">
WHEN #{item.id} THEN #{item.column_desc}
</foreach>
END,
modify_user_id = CASE id
<foreach collection="list" item="item" index="index" open="" separator="" close="">
WHEN #{item.id} THEN #{item.modify_user_id}
</foreach>
END,
modify_user_name = CASE id
<foreach collection="list" item="item" index="index" open="" separator="" close="">
WHEN #{item.id} THEN #{item.modify_user_name}
</foreach>
END,
modify_date = NOW()
WHERE
id in
<foreach collection="list" item="item" index="index" open="(" separator="," close=")">
#{item.id}
</foreach>
</update>