/* #方法一:创建表时 CREATE TABLE 表名 ( 字段名1 数据类型 [完整性约束条件…], 字段名2 数据类型 [完整性约束条件…], [UNIQUE | FULLTEXT | SPATIAL ] INDEX | KEY [索引名] (字段名[(长度)] [ASC |DESC]) ); #方法二:CREATE在已存在的表上创建索引 CREATE [UNIQUE | FULLTEXT | SPATIAL...
Re: How to limit SELECT results to unique values Tom Arnold May 27, 2014 04:16PM Re: How to limit SELECT results to unique values Phillip Ward May 28, 2014 05:04AM Sorry, you can't reply to this topic. It has been closed.Content...
INSERTINTOusers(name,email,unique_id)VALUES('Alice','alice@example.com',UUID());INSERTINTOusers(name,email,unique_id)VALUES('Bob','bob@example.com',UUID()); 1. 2. 最后,我们可以使用下面的SELECT语句来获取不同的UUID值: SELECTDISTINCTUUID()ASunique_idFROMusers; 1. 关系图 下面是users表的...
SELECTName:'SELECT'Description: Syntax:SELECT[ALL | DISTINCT | DISTINCTROW][HIGH_PRIORITY][STRAIGHT_JOIN][SQL_SMALL_RESULT][SQL_BIG_RESULT][SQL_BUFFER_RESULT]SQL_NO_CACHE[SQL_CALC_FOUND_ROWS]select_expr[, select_expr ...][FROM table_references [PARTITION partition_list][WHERE where_condition]...
ON DUPLICATE KEY UPDATE 如果插入行后会导致在一个UNIQUE索引或PRIMARY KEY中出现重复值,则执行旧行UPDATE MySQL MyIsAm 存储引擎在创建索引的时候,索引键长度是有一个较为严格的长度限制的,索引键最大长度总和不能超过1000(注意:utf8 为 3bytes),innodb 引擎则不受限制。查询系统是否支持 innodb,可以 执行如下...
Here, the SQL command selects only the unique values of age from theCustomerstable. Syntax of SQL SELECT DISTINCT SELECTDISTINCTcolumn1, column2 ...FROMtable; Here, column1, column2, ...are the table columns tableis table name from where we retrieve the distinct columns ...
INSERTINTO`choose_course`VALUES('语文','1','李雷');INSERTINTO`choose_course`VALUES('语文','1','韩梅梅');INSERTINTO`choose_course`VALUES('语文','1','露西');INSERTINTO`choose_course`VALUES('语文','2','莉莉');INSERTINTO`choose_course`VALUES('语文','2','格林');INSERTINTO`choose_cours...
CONSTRAINT "destis_einzig" UNIQUE ("einzig") ) WITH (oids = false); 上面是该表的简化版本——我跳过了不相关的字段条目。我想运行一个周期性的CRON作业,更新表中每一行center列标识的每个不同位置的天气数据(存储在Redis上)。 这里的问题在于这个词——与众不同。在一个典型的场景中,我可能有两个或多...
SQL Distinct So far we have used the select statement to retrieve all the records in a table regardless if some values repeat or not. If you wish, you can use the DISTINCT keyword to remove duplicates from your results. For instance if you wanted to just return a unique list of employees...
insert into test01 values(1,'a') ; commit; 增加索引 alter table test01 add constraint tid_pk primary key(tid) ; explain select * from (select * from test01 )t where tid =1 ; const:仅仅能查到一条数据的SQL ,用于Primary key 或unique索引 (类型 与索引类型有关) ...