/* #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...
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...
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...
[sql1]UNION [ALL | DISTINCT][sql2]UNION [ALL | DISTINCT][sql3]... sql1、sql2、sql3:平时写的查询 sql,可以连接很多条 sql ALL:可选参数,返回所有结果集,包含重复数据 distinct:可选参数,删除结果集中重复的数据(默认只写 union 也会删除重复数据,所以不加也没事) 代码语言:javascript 代码运行次数...
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 ...
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...
mysql> CREATE UNIQUE INDEX index_teacher_id_unique ON teacher(id); 4>.FULLTEXT INDEX只能创建在innodb和myisam存储引擎的CHAR,VARCHAR和TEXT字段上 5>.INDEX可以创建在包含NULL值的字段上 6>.KEY_BLOCK_SIZE=VALUE是在myisam存储引擎的表上指定索引键block大小 ...
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...
百度试题 题目SQL 语句可返回唯一不同的值的是( )。 A. SELECT ALL B. SELECT DIFFERENT C. SELECT UNIQUE D. SELECT DISTINCT 相关知识点: 试题来源: 解析 D null 反馈 收藏
SQL SELECTFirstName, LastName, BaseRate, BaseRate *40ASGrossPayFROMDimEmployeeORDERBYLastName; C. Use DISTINCT with SELECT The following example usesDISTINCTto generate a list of all unique titles in theDimEmployeetable. SQL SELECTDISTINCTTitleFROMDimEmployeeORDERBYTitle; ...