mysql left join on 與 where 篩選的差別

mysql left join   on 與 where 篩選的差別 準備兩張表: a表: id a 1 a1 2 a2 3 a3 b表: id b 1 b1 2 b2 1.沒有條件 SELECT * FROM a LEFT JOIN b ON a.id = b.id; ---------------------

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