如何使用 IF EXISTS 语句(SQL Server)从子查询中选择布尔值?
它应该是这样的:
SELECT
TABLE1.Id,
NewFiled = (IF EXISTS(SELECT Id FROM TABLE2 WHERE TABLE2.ID = TABLE1.ID)
SELECT 'TRUE'
ELSE
SELECT 'FALSE')
FROM TABLE1
Use CASE
:
SELECT
TABLE1.Id,
CASE WHEN EXISTS (SELECT Id FROM TABLE2 WHERE TABLE2.ID = TABLE1.ID)
THEN 'TRUE'
ELSE 'FALSE'
END AS NewFiled
FROM TABLE1
If TABLE2.ID
是唯一键还是主键,您也可以使用这个:
SELECT
TABLE1.Id,
CASE WHEN TABLE2.ID IS NOT NULL
THEN 'TRUE'
ELSE 'FALSE'
END AS NewFiled
FROM TABLE1
LEFT JOIN Table2
ON TABLE2.ID = TABLE1.ID
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