SQL join ON 在 Mysql 中不相等
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SQL join ON not equal in Mysql
提问by Nilesh
I have two tables. Both contains question id field. I want to get all records from first table that are not present in second one. I don't want to use "NOT IN" constrain as second table having more than 400000 records.
我有两张桌子。两者都包含问题 ID 字段。我想从第一个表中获取第二个表中不存在的所有记录。我不想使用“NOT IN”约束作为具有超过 400000 条记录的第二个表。
回答by Adriaan Stander
Try something like
尝试类似的东西
SELECt t1.*
FROM Table1 t1 LEFT JOIN
Table2 t2 ON t1.questionID = t2.questionID
WHERE t2.questionID IS NULL
回答by Lieven Keersmaekers
Typically you would do this using a LEFT JOINcombined with a WHEREclause selecting every row where the joined table returns no results.
通常，您可以使用LEFT JOIN结合WHERE子句选择连接表不返回任何结果的每一行来执行此操作。
SELECT t1.*
FROM Table1 t1
LEFT OUTER JOIN Table2 t2 ON t2.ID = t1.ID
WHERE t2.ID IS NULL
回答by Sergey Vedernikov
try:
尝试：
select from t1
right join t2 on t2.id = t1.id where t2.id is null
