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問(wèn)題描述
我在找出針對(duì)此場(chǎng)景的查詢時(shí)遇到問(wèn)題.我想在這個(gè)查詢中使用兩個(gè)表，它們是這樣的:
I'm having problems figuring out a query for this scenario. I have two tables I want to use in this query, they are like this:
Units
ID
Other Data
People
ID
UnitID <-- fk to Units
Other Data
這就是我想做的:
我想選擇在 People 表中沒(méi)有與它們鏈接的行的所有單位.我該怎么做?
This is what I want to do:
I want to select all the units that do NOT have a row in the People table linked to them. How can I do this?
推薦答案
SELECT Units.* FROM Units LEFT JOIN People ON People.UnitID = Units.ID WHERE People.ID IS NULL
或者替代
SELECT Units.* FROM Units WHERE NOT EXISTS (SELECT 1 FROM People WHERE People.UnitID = Units.ID)
甚至
SELECT Units.* FROM Units WHERE Units.ID NOT IN (SELECT UnitID FROM People)
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