Question

我试图在PostgreSQL 9.2中执行以下SQL语句，但它失败并出现错误：

SELECT "TrainingName" FROM "HSETrainingName" WHERE "ID" = 
SELECT "trainingID" FROM "HSEGroupedTraining" WHERE "groupID" =3

第二个select语句返回多个值。怎么解决？

Answer 1

您可以使用IN构建：

SELECT "TrainingName" 
  FROM "HSETrainingName" 
 WHERE "ID" IN (SELECT "trainingID" 
                  FROM "HSEGroupedTraining" 
                 WHERE "groupID" = 3)

Answer 2

使用子查询和IN：

SELECT "TrainingName" 
FROM "HSETrainingName" 
WHERE "ID" IN
(SELECT "trainingID" 
FROM "HSEGroupedTraining" 
WHERE "groupID" =3)

SELECT基于多结果条件

2 个答案: