1.7 连接列值

Q: 将多列值连接作为一列返回
A: 使用内置函数 "concat"

DB2, Oracle, PostgreSQL ( concat函数，以及简写 "||" 双竖线连接符 )
SELECT ename || ' WORKS AS A ' || job AS msg
FROM emp
WHERE deptno = 10

MySQL ( concat函数 )
SELECT concat(ename, ' WORKS AS A ', job) AS msg
FROM emp
WHERE deptno = 10

SQL Server ( "+" 运算符连接)
SELECT ename + ' WORKS AS A ' + job AS msg
FROM emp
WHERE deptno = 10

+---------------------------+
| msg |
+---------------------------+
| CLARK WORKS AS A MANAGER |
| KING WORKS AS A PRESIDENT |
| MILLER WORKS AS A CLERK |
+---------------------------+
3 rows in set (0.04 sec)

Tables Used:
for MySQL
http://www.hooto.com/home/rui/doc/archives/5089.html
for PostgreSQL
http://www.hooto.com/home/rui/doc/archives/5090.html

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