日期:2014-05-16  浏览次数:20940 次

mysql 两表排重
两个表的数据大概都在100W 表A 和表B 排重要根据3个字段 a,b,c这三个字段都相同才排重a表中的

------解决方案--------------------
贴建表及插入记录的SQL,及要求结果出来看看
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python:
SELECT1="select a,b,c from A";
cur.execute(SELECT1)
result1=cur.fetchall()
SELECT2="select * from B where a=%s and b=%s and c=%c"
cur.execut(SELECT2,result1)
result2=cur.execute(SELECT2)
if result2 != ():
DELETE="delete * from B where a=%s and b=%s and c=%c"
cur.execute(DELETE,result1)
------解决方案--------------------
delete from a where exists (select 1 from b where a=a.a and b=a.b and c=a.c);

或者

delete a from a inner join b on a.a=b.a and a.b=b.b and a.c=b.c;

不过需要有索引(a,b,c)