MySQL Basics (vi) SELECT statement

Single-table query: &NBSP;&NBSP;&NBSP;&NBSP;SELECT&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;&NBSP;[&NBSP;DISTINCT&NBSP;]         [SQL_CACHE | SQL_NO_CACHE]     &NBSP;&NBSP;&NBSP;&NBSP;SELECT_EXPR&NBSP;[,SELECT_EXPR&NBSP, ...]         [from table_references [ where where_ condition ]        [group by {col_name | expr  |}]  [HAVING where_condition] [ORDER BY [ASC | DESC]]   DISTINCT: Data deduplication sql_cache: Specify cache sql_no_cache: Specify cache     where clause: Specify conditions to implement filter filter conditions:      Arithmetic Arithmetic:+   -   *   /   %  >   <  >=  <=     logical operations: and: With operations   or: or operations    not: Non-arithmetic      character comparison:=  !=         list elements Comparison:in  (element 1, Element 2, Element 3,...)     is null: Empty     is not null: Non-empty      Like: fuzzy matching, can not use as much as possible     rlike: based on regular fuzzy matching, can not use as much as possible     GROUP  By clause: More specified conditions to group matching results, implementing "aggregation" operations          common functions:     SUM (condition) #求和             max (condition) #最大值      min (condition) #最小值     avg (condition) #平均值     count (condition) #统计记录数   & Nbsp; having: Example of filtering the results after Group by:    mysql> create database  MyDB, #创建测试数据库     mysql> USE mydb;    mysql>  create table test  (Id int), Name varchar (2), Qq int (Gender char) Create a test table     mysql> INSERT INTO Test values (1, ' Zhangshan ', 12345, ' F ');     #插入测试数据     mysql>  insert into test values (2, ' Lisi ', 123142, ' F ');    mysql>  Insert into test values (3, ' ZSF ', 124312, ' M ');    mysql> insert  Into test values (4, ' yyy ', 124312, ' F ');    mysql> insert into  Test values (5, ' Ytt ', 124312, ' M ');     single-table Query example:    mysql>  select * from test where id>2 and id<5; #查询ip大于2小于5的数据      mysql> SELECT * FROM test WHERE id>2 GROUP BY  gender; #对性别进行分组     mysql> select sum (ID),gender from test  group by gender; #对性别进行分组, and begged for the sum of their IDs     mysql> select * from  test group by gender having id>2; #对性别进行分组, display group          Multi-Table association queries with IDs greater than 2:     mysql> CREATE TABLE test2  (Emain varchar ($), Age int (10)); #创建测试环境     mysql> insert into test2 values (' [email protected] ' ,     mysql> insert into test2 values (' [email protected] ',     mysql> insert into test2 values (' [email protected] ', 20 );     mysql> select test.id,test2.age from test,test2 where  test.id>2 and test2.age>10;    test.id# the ID field of the first chapter table test2.age# Chapter II of the Age field test# first chapter table   table name test2# chapter II table   table name test.id>2 and test2.age# stitching displays the ID field of test and the age field of Test2. However, the ID field of test must be greater than 2 and the age field of test2 must be greater than 10    mysql> select * from test. Test2 where test.id>2 AND test2.age>10;     #拼接显示test, all fields of test2, However, the ID field of test must be greater than 2 and the age field of test2 must be greater than 10

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MySQL Basics (vi) SELECT statement