第 5 章 排序检索数据
5.1 排序数据
输入: SELECT help_category.name FROM help_category ORDER BY help_category.name;
输出:
+---------------------------------------+
| name |
+---------------------------------------+
| Account Management |
| Administration |
| Aggregate Functions and Modifiers |
| Bit Functions |
| Cast Functions and Operators |
| Comparison Operators |
| Components |
| Compound Statements |
| Contents |
| Data Definition |
| Data Manipulation |
| Data Types |
| Date and Time Functions |
| Encryption Functions |
| Enterprise Encryption Functions |
| Flow Control Functions |
| Functions |
| Geographic Features |
| Geometry Constructors |
| Geometry Property Functions |
| Geometry Relation Functions |
| GeometryCollection Property Functions |
| GROUP BY Functions and Modifiers |
| GTID |
| Help Metadata |
| Information Functions |
| Internal Functions |
| Language Structure |
| LineString Property Functions |
| Loadable Functions |
| Locking Functions |
| Logical Operators |
| MBR |
| MBR Functions |
| Miscellaneous Functions |
| Numeric Functions |
| Performance Schema Functions |
| Plugins |
| Point Property Functions |
| Polygon Property Functions |
| Prepared Statements |
| Replication Statements |
| Spatial Functions |
| Storage Engines |
| String Functions |
| Table Maintenance |
| Transactions |
| Utility |
| Window Functions |
| WKB Functions |
| WKT |
| WKT Functions |
| XML |
+---------------------------------------+
分析: order by 子句用于对查询结果进行排序，默认升序
5.2 按多个列排序
输入: SELECT help_category_id,help_category.name,parent_category_id FROM help_category ORDER BY help_category.name;
输出:
+------------------+---------------------------------------+--------------------+
| help_category_id | name | parent_category_id |
+------------------+---------------------------------------+--------------------+
| 46 | Account Management | 0 |
| 3 | Administration | 0 |
| 34 | Aggregate Functions and Modifiers | 4 |
| 18 | Bit Functions | 4 |
| 16 | Cast Functions and Operators | 4 |
| 10 | Comparison Operators | 4 |
| 49 | Components | 0 |
| 45 | Compound Statements | 0 |
| 0 | Contents | 0 |
| 40 | Data Definition | 0 |
| 41 | Data Manipulation | 0 |
| 2 | Data Types | 0 |
| 14 | Date and Time Functions | 4 |
| 19 | Encryption Functions | 4 |
| 5 | Enterprise Encryption Functions | 4 |
| 12 | Flow Control Functions | 4 |
| 4 | Functions | 0 |
| 7 | Geographic Features | 0 |
| 25 | Geometry Constructors | 22 |
| 26 | Geometry Property Functions | 22 |
| 31 | Geometry Relation Functions | 22 |
| 30 | GeometryCollection Property Functions | 22 |
| 35 | GROUP BY Functions and Modifiers | 4 |
| 33 | GTID | 4 |
| 1 | Help Metadata | 0 |
| 21 | Information Functions | 4 |
| 38 | Internal Functions | 4 |
| 6 | Language Structure | 0 |
| 28 | LineString Property Functions | 22 |
| 48 | Loadable Functions | 0 |
| 20 | Locking Functions | 4 |
| 11 | Logical Operators | 4 |
| 8 | MBR | 7 |
| 32 | MBR Functions | 22 |
| 39 | Miscellaneous Functions | 4 |
| 13 | Numeric Functions | 4 |
| 37 | Performance Schema Functions | 4 |
| 50 | Plugins | 0 |
| 27 | Point Property Functions | 22 |
| 29 | Polygon Property Functions | 22 |
| 44 | Prepared Statements | 0 |
| 43 | Replication Statements | 0 |
| 22 | Spatial Functions | 4 |
| 52 | Storage Engines | 0 |
| 15 | String Functions | 4 |
| 47 | Table Maintenance | 0 |
| 42 | Transactions | 0 |
| 51 | Utility | 0 |
| 36 | Window Functions | 4 |
| 24 | WKB Functions | 22 |
| 9 | WKT | 7 |
| 23 | WKT Functions | 22 |
| 17 | XML | 4 |
+------------------+---------------------------------------+--------------------+
5.3 指定排序方向
输入: SELECT help_category.name FROM help_category ORDER BY help_category.name DESC;
输出:
+---------------------------------------+
| name |
+---------------------------------------+
| XML |
| WKT Functions |
| WKT |
| WKB Functions |
| Window Functions |
| Utility |
| Transactions |
| Table Maintenance |
| String Functions |
| Storage Engines |
| Spatial Functions |
| Replication Statements |
| Prepared Statements |
| Polygon Property Functions |
| Point Property Functions |
| Plugins |
| Performance Schema Functions |
| Numeric Functions |
| Miscellaneous Functions |
| MBR Functions |
| MBR |
| Logical Operators |
| Locking Functions |
| Loadable Functions |
| LineString Property Functions |
| Language Structure |
| Internal Functions |
| Information Functions |
| Help Metadata |
| GTID |
| GROUP BY Functions and Modifiers |
| GeometryCollection Property Functions |
| Geometry Relation Functions |
| Geometry Property Functions |
| Geometry Constructors |
| Geographic Features |
| Functions |
| Flow Control Functions |
| Enterprise Encryption Functions |
| Encryption Functions |
| Date and Time Functions |
| Data Types |
| Data Manipulation |
| Data Definition |
| Contents |
| Compound Statements |
| Components |
| Comparison Operators |
| Cast Functions and Operators |
| Bit Functions |
| Aggregate Functions and Modifiers |
| Administration |
| Account Management |
+---------------------------------------+
分析: 如果你想按照降序顺序排序，可以添加 desc 关键字在列名后面
例如: 使用 order by 和 LIMIT 的组合，能够找到一个列中最高或最低值
