inner join(等值连接) 只返回两个表中联结字段相等的行 left join(左联接) 返回包括左表中的所有记录和右表中联结字段相等的记录 right join(右联接) 返回包括右表中的所有记录和左表中联结字段相等的记录 INNER JOIN 语法: INNER JOIN 连接两个数据表的用法: SELECT * FROM 表1 INNER JOIN 表2 ON 表1....
LEFT OUTER JOIN 或 LEFT JOIN RIGHT OUTER JOIN 或 RIGHT JOIN FULL OUTER JOIN 或 FULL JOIN SQL Server 支持 SQL-92 外联接语法,以及在 WHERE 子句中使用 *= 和 =* 运算符指定外联接的旧式语法。由于 SQL-92 语法不容易产生歧义,而旧式 Transact-SQL 外联接有时会产生歧义,因此建议使用 SQL-92 语法。
Inner Join(内连接查询): 概念:与Join相同,两表或多表之间联立查询数据,因此我们在使用多表join查询的时候既可以使用where关联,也可以是inner join关联查询 代码语言:javascript 复制 select*from Students s inner join Class c on s.ClassId=c.ClassId Left Join(左连接查询): 概念:以左表中的数据为主,即使...
select * from Customer cswhere cs.Group_No = '册本编号' andcs.Customer_No in ( select Customer_No from Customer cs left join Meter me on cs.Customer_No = me.Customer_No inner join Meter_data md on me.meter_no = md.meter_no and md.date = '2019-04-09' where cs.Group_NO='册...
JOIN(连接) JOIN 用于根据两个或多个表中的列之间的关系(这些表之间的共同字段),连接起来,从这些表中查询数据。 INNER JOIN(表中至少一个匹配) 在表中存在至少一个匹配时,INNER JOIN 关键字返回行。 注意:INNER JOIN 与 JOIN 是相同的。
LEFT JOIN:即使右表中没有匹配,也从左表返回所有的行; RIGHT JOIN:即使左表中没有匹配,也从右表返回所有的行; FULL JOIN:只要其中一个表中存在匹配,则返回行。 图片来自于RUNOOB,侵删 一、SQL INNER JOIN 关键字 INNER JOIN 其实与JOIN是相同的,主要用于在表中至少一个匹配时返回行。具体的语法如下: ...
文末有数据库sql@[toc] 表数据 新建了俩张表 SQL查询 inner join 求交集 SELECT * FROM user1 a INNER JOIN user2 ...
// Join the two data sources based on a composite key consisting of first and last name,// to determine which employees are also students.IEnumerable<string> query =fromteacherinteachersjoinstudentinstudentsonnew{ FirstName = teacher.First, LastName = teacher.Last }equalsnew{ student.FirstName...
// Join the two data sources based on a composite key consisting of first and last name,// to determine which employees are also students.IEnumerable<string> query =fromteacherinteachersjoinstudentinstudentsonnew{ FirstName = teacher.First, LastName = teacher.Last }equalsnew{ student.FirstName...
SQL LEFT JOIN KeywordThe LEFT JOIN keyword returns all records from the left table (table1), and the matching records from the right table (table2). The result is 0 records from the right side, if there is no match.LEFT JOIN SyntaxSELECT column_name(s) FROM table1 LEFT JOIN table2 ...