修改SQL语句以添加表中的列

Question

我有两个表： TrainingMatrix和Data 。 对于TrainingMatrix我有以下SQL语句：

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

每个工资单编号都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，以便可以显示/投影"EmployeeName"及其结果。

我使用PostgreSQL 9.2和pgAdmin III。

Answer 1

您可以将查询与Data表连接起来：

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;