SQL CONCAT 函数
CONCAT 函数用于将两个字符串连接为一个字符串,试一下下面这个例子:
SQL> SELECT CONCAT('FIRST ', 'SECOND');
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| CONCAT('FIRST ', 'SECOND') |
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| FIRST SECOND |
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1 row in set (0.00 sec)
要对 CONCAT 函数有更为深入的了解,请考虑 employee_tbl 表,表中记录如下所示:
SQL> SELECT * FROM employee_tbl;
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| id | name | work_date | daily_typing_pages |
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| 1 | John | 2007-01-24 | 250 |
| 2 | Ram | 2007-05-27 | 220 |
| 3 | Jack | 2007-05-06 | 170 |
| 3 | Jack | 2007-04-06 | 100 |
| 4 | Jill | 2007-04-06 | 220 |
| 5 | Zara | 2007-06-06 | 300 |
| 5 | Zara | 2007-02-06 | 350 |
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7 rows in set (0.00 sec)
现在,假设你想要将上表中所有的姓名(name)、id和工作日(work_date)连接在一起,那么可以通过如下的命令来达到目的:
SQL> SELECT CONCAT(id, name, work_date)
-> FROM employee_tbl;
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| CONCAT(id, name, work_date) |
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| 1John2007-01-24 |
| 2Ram2007-05-27 |
| 3Jack2007-05-06 |
| 3Jack2007-04-06 |
| 4Jill2007-04-06 |
| 5Zara2007-06-06 |
| 5Zara2007-02-06 |
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7 rows in set (0.00 sec)