修改SQL语句以附加表中的列

Question

我有两个表：TrainingMatrix和Data。对于TrainingMatrix我有这个SQL语句：

SELECT DISTINCT ON (payroll, "TrainingName", "Institute") *
            FROM   "TrainingMatrix" 
            ORDER  BY payroll, "TrainingName", "Institute" ,"TrainingDate" DESC NULLS LAST;

每个工资单号与唯一的员工姓名相关。因此，在Data表中，我有两列：payroll和"EmployeeName"。如何修改前面的语句，以便我也可以显示/项目"EmployeeName"。

我使用PostgreSQL 9.2和pgAdmin III。

Answer 1

您可以使用Data表格加入查询：

SELECT DISTINCT ON ("TrainingMatrix".payroll, "TrainingName", "Institute") "Data".EmployeeName, "TrainingMatrix".*
FROM "TrainingMatrix" 
JOIN "Data" ON "TrainingMatrix".payroll = "Data".payroll
ORDER  BY payroll, "TrainingName", "Institute" ,"TrainingDate" DESC NULLS LAST;