sql - 修改 SQL 语句以从表中追加列

Question

我有两张桌子：TrainingMatrix和Data。因为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;

每个工资单号都与一个唯一的员工姓名相关联。所以，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/投影"EmployeeName"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;