如果表B的数据是 COLUMN b COLUMN c 1 X 1 XX 2 AX 2 XA 返回结果是: a b c 1 2 ????????????????
看是否是你要的结果: select distinct a.*, greatest(b.b, null), greatest(b.c, null) from a left join b on a.a = b.b;
select distinct a.*, greatest(b.b, null), greatest(b.c, null) from a left join b on a.a = b.b;
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