sql - 如何在 postgreSQL 的一行中获取多个值？

Question

我在 postgreSQL9.4 中有数据库表名 emp_leave，比如

|emp_name|leave_type|total_lday|
| Tame   |    PL    |     3    |
| Tame   |    UL    |     4    |

我想要这样的查询结果

|emp_name|paid_leave|unpaid_leave|
| Tame   |    3     |      4     |    

Answer 1

Postgresql 9.4 也有 FILTER 子句来做条件聚合:

select emp_name, 
       max(total_lday) FILTER (where leave_type = 'PL') as paid_leave,
       max(total_lday) FILTER (where leave_type = 'UL') as unpaid_leave
from emp_leave
group by emp_name

(ANSI SQL-2016，功能 T612，“高级 OLAP 操作”。)