AS 的 SQL 语法错误

Question

我对 SQL 不太熟悉，并且遇到此查询的语法错误。我怀疑我可能错误地使用了“AS”关键字。谁能在这里检查我的语法？我还尝试使用 [] 代替单引号。谢谢!

SELECT m.dname, COUNT(*) AS 'Total Students', AVG(s.age) AS 'Average Age', 
AVG(s.gpa) AS 'Average GPA'
FROM student s JOIN major m
ON s.sid = m.sid
GROUP BY m.dname
HAVING COUNT(*) >= 3

编辑 ****

我得到的错误:

ERROR: syntax error at or near "'Total Students'" LINE 1: SELECT m.dname, COUNT(*) AS 'Total Students', AVG(s.age) AS... ^

使用 PostgreSQL 数据库

Answer 1

在 postgres 中，对于包含空格的列别名，使用双引号，而不是单引号:

SELECT m.dname, COUNT(*) AS "Total Students", AVG(s.age) AS "Average Age", 
AVG(s.gpa) AS "Average GPA"
FROM student s JOIN major m
ON s.sid = m.sid
GROUP BY m.dname
HAVING COUNT(*) >= 3

-- http://www.postgresql.org/docs/9.2/static/sql-select.html#SQL-SELECT-LIST