SQL ：将 2 个语句与 2 个 SELECT 组合

Question

如何将这 2 个 SQL 语句合并为一个？

我想在此处替换值 shape：

SELECT path[1] AS number, st_x(geom), st_y(geom) 
FROM st_dumppoints(shape)

通过这个 :

SELECT shape 
FROM tableA 
WHERE id = 'test'

像这样：

SELECT path[1] AS number, st_x(geom), st_y(geom) 
FROM st_dumppoints(SELECT shape FROM tableA WHERE id = 'test')

Answer 1

只需在子选择周围添加一对额外的括号。从语法上讲，子查询需要括号，函数调用也需要，所以你最终得到

FROM st_dumppoints((SELECT shape FROM tableA WHERE id = 'test'))

注意，如果子查询returns多于一行，语句会报错。

SQL : combine 2 statements with 2 SELECT