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[英]How to select all records from one table that do not exist in another table for certain condition in another table?
[英]how to select all records from one table that not exist in relation table?
對象類 1
OBID | Name
0001 | ob01
0002 | ob02
關系1
RELID|LEFTOBID|RIGHTOBID|CLASS1|CLASS2
R001 |0001 |000X |ObjectClass1|ObjectClass2
現在我想知道的是如何編寫查詢以找出 OBID 0002 不存在關系
使用not exists
為:
select *
from ObjectClass1 o
where not exists
( select 1 from Relation1 r where r.LEFTOBID = o.OBID );
SQL
SELECT *
FROM ObjectClass1 obj
LEFT JOIN
Relation1 rel
on obj.OBID = rel.LEFTOBID
WHERE rel.LEFTOBID is null
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