Sql 基于多结果条件选择
我试图在PostgreSQL 9.2中执行以下SQL语句,但失败并出现错误:Sql 基于多结果条件选择,sql,database,postgresql,Sql,Database,Postgresql,我试图在PostgreSQL 9.2中执行以下SQL语句,但失败并出现错误: SELECT "TrainingName" FROM "HSETrainingName" WHERE "ID" = SELECT "trainingID" FROM "HSEGroupedTraining" WHERE "groupID" =3 第二个select语句返回多个值。如何解决它?您可以在构造中使用: SELECT "TrainingName" FROM "HSETrainingName" WH
SELECT "TrainingName" FROM "HSETrainingName" WHERE "ID" =
SELECT "trainingID" FROM "HSEGroupedTraining" WHERE "groupID" =3
第二个select语句返回多个值。如何解决它?您可以在
构造中使用:
SELECT "TrainingName"
FROM "HSETrainingName"
WHERE "ID" IN (SELECT "trainingID"
FROM "HSEGroupedTraining"
WHERE "groupID" = 3)
将子查询与中的一起使用:
SELECT "TrainingName"
FROM "HSETrainingName"
WHERE "ID" IN
(SELECT "trainingID"
FROM "HSEGroupedTraining"
WHERE "groupID" =3)
... 哪个PostgreSQL可能会转换为联接,这是形成查询的另一种方式—介于HSETrainingName
和HSEGroupedTraining
之间的内部联接。