MySql-Mysql技术内幕~SQL编程学习笔记（N）

1、_rowid

  类似Oracle的rowid

mysql> select _rowid rowid,t.* from city t limit 10;
+-------+----+----------------+-------------+---------------+------------+
| rowid | ID | Name           | CountryCode | District      | Population |
+-------+----+----------------+-------------+---------------+------------+
|     1 |  1 | Kabul          | AFG         | Kabol         |    1780000 |
|     2 |  2 | Qandahar       | AFG         | Qandahar      |     237500 |
|     3 |  3 | Herat          | AFG         | Herat         |     186800 |
|     4 |  4 | Mazar-e-Sharif | AFG         | Balkh         |     127800 |
|     5 |  5 | Amsterdam      | NLD         | Noord-Holland |     731200 |
|     6 |  6 | Rotterdam      | NLD         | Zuid-Holland  |     593321 |
|     7 |  7 | Haag           | NLD         | Zuid-Holland  |     440900 |
|     8 |  8 | Utrecht        | NLD         | Utrecht       |     234323 |
|     9 |  9 | Eindhoven      | NLD         | Noord-Brabant |     201843 |
|    10 | 10 | Tilburg        | NLD         | Noord-Brabant |     193238 |
+-------+----+----------------+-------------+---------------+------------+
rows in set (0.00 sec)

mysql>

 2、查看表结构

mysql> show create table tG;
*************************** 1. row ***************************
       Table: t
Create Table: CREATE TABLE `t` (
  `a` int(10) unsigned DEFAULT NULL,
  `b` int(10) unsigned DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8
1 row in set (0.00 sec)

ERROR:
No query specified

mysql> desc t;
+-------+------------------+------+-----+---------+-------+
| Field | Type             | Null | Key | Default | Extra |
+-------+------------------+------+-----+---------+-------+
| a     | int(10) unsigned | YES  |     | NULL    |       |
| b     | int(10) unsigned | YES  |     | NULL    |       |
+-------+------------------+------+-----+---------+-------+
2 rows in set (0.00 sec)

mysql>

 3、hex函数

 4、SQL_MODE：SQL模式

5、MySQL中的函数

  1》cast：强制转换

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