2. 第二种方法为在query方法中使用 nestTables属性,并将属性值设置为true。因此会将两个表中的数据以两个对象的形式输出来。如下sql语句改为如下: { sql: 'select * from user inner join user2 where user.age = user2.age', nestTables: true } 1. 2. 3. 4. 代码如下:
交叉连接,得到的结果是两个表的乘积; 效果和 inner join 类似,如下所示: 回到顶部 五:union操作 select * from user left join user2 on user.username = user2.username union select * from user right join user2 on user.username = user2.username; 上面代码的含义是:查询user表和user2表,如果该两张...
#2.内连接:INNER JOIN ·内连接INNER JOIN是最常用的连接操作。 ·从数学的角度讲就是求两个表的交集,从笛卡尔积的角度讲就是从笛卡尔积中挑出ON子句条件成立的记录。 有INNER JOIN,WHERE(等值连接),STRAIGHT_JOIN,JOIN(省略INNER)四种写法。 SELECT * FROM t_blog INNER JOIN t_type ON t_blog.typeId=t_...
mysql>selecte.empno,e.ename,d.dnamefromemp einnerjoindept done.deptno=d.deptno;+---+---+---+|empno|ename|dname|+---+---+---+|1|aa|FINANCE||2|bb|HR||3|cc|SALES||5|ee|SALES||6|ff|HR|+---+---+---+ INNER JOIN就是求取2个表的共有数据(交集),我们可以这样来理解表INNER...
SELECT*FROMperson pINNERJOINcar cONp.id=c.idINNERJOINhouse hONc.id=h.id; SQL Copy LEFT JOIN 在LEFT JOIN操作中,左侧表的所有行都会被保留,而右侧表只有符合连接条件的行才会被保留。如果在右侧表中没有相应的行,则填充NULL值。 示例代码如下: ...
1. INNER JOIN（内连接）内连接返回两个表中匹配的行。如果表中有至少一个匹配，则返回行。SELECT ...
The statement must not use theSTRAIGHT_JOINjoin type in the outer query. TheSTRAIGHT_JOINmodifier must not be present. The number of outer and inner tables together must be less than the maximum number of tables permitted in a join.
除此之外,我在Mysql官网上还看到一段话(参考博客2): When the optimizer evaluates plans for outer join operations, it takes into consideration only plans where, for each such operation, the outer tables are accessed before the inner tables. The optimizer choices are limited because only such plans...
不同类型的JOIN用于实现不同的数据表连接需求，有助于实现复杂的查询。The JOIN types in MySQL primarily include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN, and their respective roles are as follows:INNER JOIN (Inner Join):Returns matching rows from both tables based on the join ...
SELECTt1.id,t2.id,desc1,desc2,desc3,desc4FROMt1INNERJOINt2ONt1.id=t2.id; 所以,我怀疑是否因为sql_mode没有开启为严格模式导致的? 代码语言:javascript 代码运行次数:0 运行 AI代码解释 SET@session.sql_mode='STRICT_TRANS_TABLES'; 开启严格模式,继续查询都没问题,所以mysql的语法还是相对没那么严格...