Tag：mysqlnotnull
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Solution to the problem that not in is null in MySQL
Some time ago, when I was doing a small function in the company, I counted the number of data in a certain situation and then modified the problem. At that time, I thought it was very simple. I wrote the following SQL: SELECT COUNT(*) FROM t1 where tl.c1 not IN (SELECT t2.c1 FROM t2); The […]