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例如我有2个查询:这些查询是否相同?
1)
SELECT * FROM unit
INNER JOIN entity
WHERE unit.length = entity.length
2)
SELECT * FROM unit
INNER JOIN entity ON entity.length = unit.length
是这些查询等效?
例如我有2个查询:这些查询是否相同?
1)
SELECT * FROM unit
INNER JOIN entity
WHERE unit.length = entity.length
2)
SELECT * FROM unit
INNER JOIN entity ON entity.length = unit.length
是这些查询等效?
是的,这两个查询都会产生相同的结果。
是的,如果第一次工作。从我看来,首先应该是'SELECT * FROM unit,entity WHERE unit.length = entity.length',但这是可怕的代码风格。 – degr
Dupe train:https://stackoverflow.com/questions/44917/explicit-vs-implicit-sql-joins,https://stackoverflow.com/questions/1018822/inner-join-on-vs-where-clause, https://stackoverflow.com/questions/354070/sql-join-where-clause-vs-on-clause?rq=1 .. –
感谢大家,是的,它是一个重复的,下次我会更仔细地看 –