批量更新mysql表数据

1、批量更新表中某个字段，如果表比较大，每条记录都执行一条update，1s执行10条数据，10万条数据就要1W秒，3个多小时。

2、可以用case when 来实现，模板如下

UPDATE categories SET 
display_order = CASE id 
        WHEN 1 THEN 3 
        WHEN 2 THEN 4 
        WHEN 3 THEN 5 
END
WHERE id IN (1,2,3);

ID 是条件字段，WHEN 相当于where，THEN 表示要更新的字段设置成的值。

如果有多个字段要更新，模板如下

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)

手动串接字符太麻烦，可以用python，每串接2000条，执行一次sql，1分钟内解决问题：

sql = " SELECT `id`,c_id,SUM(`total_price` - `reduction`) AS price FROM `orders` WHERE STATUS IN (9,11) AND total_price >0 GROUP BY c_id  HAVING price > 0 ORDER BY c_id"
datas = bt.getData(sql)

error = 0
count = 0
totalcount = 0
id = []
sql = "UPDATE customer SET consumption_amount = consumption_amount + CASE id "
sqlwhen = ""
sqlend = "END WHERE id in "
sqllen = 2000

with open("sqlupdatenew.sql",'w') as f:
    print(len(datas))
    for data in datas:
        if count <= sqllen:
            sqlwhen += "WHEN " + str(data[1]) + " THEN " + str(data[2]) + " "
            count += 1
            id.append(data[1])

        if count == sqllen or totalcount == len(datas) -1:
            mysql = sql + sqlwhen + sqlend + str(tuple(id))
            bt.executesql(mysql)
            temp = sql + sqlwhen + sqlend + str(tuple(id)) + ";
"
            f.write(temp)
            print(totalcount)
            count = 0
            sqlwhen = ""
            id.clear()

        totalcount += 1


bt.closemysql()