1.help select
- mysql> help select
- Name: 'SELECT'
- Description:
- Syntax:
- SELECT
- [ALL | DISTINCT | DISTINCTROW ]
- [HIGH_PRIORITY]
- [STRAIGHT_JOIN]
- [SQL_SMALL_RESULT] [SQL_BIG_RESULT] [SQL_BUFFER_RESULT]
- [SQL_CACHE | SQL_NO_CACHE] [SQL_CALC_FOUND_ROWS]
- select_expr [, select_expr ...]
- [FROM table_references
- [PARTITION partition_list]
- [WHERE where_condition]
- [GROUP BY {col_name | expr | position}
- [ASC | DESC], ... [WITH ROLLUP]]
- [HAVING where_condition]
- [ORDER BY {col_name | expr | position}
- [ASC | DESC], ...]
- [LIMIT {[offset,] row_count | row_count OFFSET offset}]
- [PROCEDURE procedure_name(argument_list)]
- [INTO OUTFILE 'file_name'
- [CHARACTER SET charset_name]
- export_options
- | INTO DUMPFILE 'file_name'
- | INTO var_name [, var_name]]
- [FOR UPDATE | LOCK IN SHARE MODE]]
- SELECT is used to retrieve rows selected from one or more tables, and
- can include UNION statements and subqueries. See [HELP UNION], and
- http://dev.mysql.com/doc/refman/5.6/en/subqueries.html.
- The most commonly used clauses of SELECT statements are these:
- o Each select_expr indicates a column that you want to retrieve. There
- must be at least one select_expr.
- o table_references indicates the table or tables from which to retrieve
- rows. Its syntax is described in [HELP JOIN].
- o Starting in MySQL 5.6.2, SELECT supports explicit partition selection
- using the PARTITION keyword with a list of partitions or
- subpartitions (or both) following the name of the table in a
- table_reference (see [HELP JOIN]). In this case, rows are selected
- only from the partitions listed, and any other partitions of the
- table are ignored. For more information and examples, see
- http://dev.mysql.com/doc/refman/5.6/en/partitioning-selection.html.
- In MySQL 5.6.6 and later, SELECT ... PARTITION from tables using
- storage engines such as MyISAM that perform table-level locks (and
- thus partition locks) lock only the partitions or subpartitions named
- by the PARTITION option.
- See
- http://dev.mysql.com/doc/refman/5.6/en/partitioning-limitations-locki
- ng.html, for more information.
- o The WHERE clause, if given, indicates the condition or conditions
- that rows must satisfy to be selected. where_condition is an
- expression that evaluates to true for each row to be selected. The
- statement selects all rows if there is no WHERE clause.
- In the WHERE expression, you can use any of the functions and
- operators that MySQL supports, except for aggregate (summary)
- functions. See
- http://dev.mysql.com/doc/refman/5.6/en/expressions.html, and
- http://dev.mysql.com/doc/refman/5.6/en/functions.html.
- SELECT can also be used to retrieve rows computed without reference to
- any table.
- URL: http://dev.mysql.com/doc/refman/5.6/en/select.html
select user();
3. 指定查询条件, 使用数据过滤的更加准确
- select user,host,password from mysql.user;
4. 模糊查询
- select user,host,password from mysql.user where user like 'roo%';
5. 排序 order by
- --降序排列
- select * from anyuxweb.t2 order by id desc;
- --升序排列
- select * from anyuxweb.t2 order by id asc;
6.limit 使用
- select * from anyuxweb.t2 order by id asc limit 1,2;