7、OUTER JOIN EXCLUDING INNER JOIN(外连接-内连接) mysql> select a.user_id, name, age -> from table_name as a left join table_age as b -> on a.user_id =b.user_id -> where b.user_id is null -> union -> select b.user_id, name, age -> from table_name as a right join ...
This Join can also be referred to as aFULL OUTER JOINor aFULL JOIN. This query will return all of the records from both tables, joining records from the left table (table A) that match records from the right table (table B). This Join is written as follows: Collapse |Copy Code SELEC...
.. FROM table_name [JOIN table_name2 ON join_condition] [WHERE condition] [GROUP BY column(s)] [HAVING group_condition] [ORDER BY column(s) [ASC|DESC]] [LIMIT offset, row_count];查询所有记录代码语言:sql AI代码解释 SELECT * FROM students;...
TheFULL JOINorFULL OUTER JOINkeyword is used to select all records from the left table and right table. It combines both tables into a result-set and returns it to the user. Note that MySQLFULL JOINis known to create large datasets. It works like theunion operationyou would have seen in...
代码语言:javascript 代码运行次数:0 运行 AI代码解释 CREATE TABLE logs ( id INT, json_data JSON ) ENGINE=InnoDB; SELECT * FROM logs WHERE JSON_CONTAINS_PATH(json_data, 'one', '$.user'); 窗口函数优化: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 SELECT user_id, COUNT(*) OVER (...
type optimizationisused most ofteninresolving subqueries.Inthe following examples, MySQL canusea ref_or_nulljointoprocess ref_table: 这种连接类型与ref类似,但是除此之外,MySQL还对包含NULL值的行进行额外的搜索。 这种连接类型优化最常用于解析子查询。 在以下示例中,MySQL可以使用ref_or_null连接来处理ref_ta...
ON table_name1.column_name=table_name2.column_name 1. 2. 3. 4. 注释:在某些数据库中, LEFT JOIN 称为 LEFT OUTER JOIN。 SQL RIGHT JOIN 关键字 RIGHT JOIN 关键字会右表 (table_name2) 那里返回所有的行,即使在左表 (table_name1) 中没有匹配的行。
drop table stu; 运行效果展示:五、数据表的约束 为防止错误的数据被插入到数据表,MySQL中定义了一些维护数据库完整性的规则;这些规则常称为表的约束。常见约束如下:1.主键约束 主键约束即primary key用于唯一的标识表中的每一行。被标识为主键的数据在表中是唯一的且其值不能为空。这点类似于我们每个人都有一...
INNER JOIN: Returns records that have matching values in both tables LEFT JOIN: Returns all records from the left table, and the matched records from the right table RIGHT JOIN: Returns all records from the right table, and the matched records from the left table CROSS JOIN: Returns all ...
简介：内表基于索引分组，然后与外表进行join。匹配成功后，提取外表记录并继续处理下一个分组。特点：执行计划中会标注last semijoin table的looseScan标记，通过分组和索引优化匹配过程。Materialize scan/Materialize lookup策略：简介：将内表物化成临时表，通过扫描或查找物化表来避免重复记录。特点：...