Inner Join with NATURAL clause behaves like CROSS JOIN Code: SELECT*FROMcustomerNATURALINNERJOINitem; Copy Output: Explanation In the above example, there are no matching rows between the participating tables; so all the columns appear in this join and it behaves like a cross join. Previous:CROS...
The following example uses INNER JOIN clauses to retrieve data from three tables SELECT c.customer_id, c.first_name || ' ' || c.last_name customer_name, s.first_name || ' ' || s.last_name staff_name, p.amount, p.payment_date FROM customer c INNER JOIN payment p USING (customer...
1.1 常见连接类型 INNER JOIN(内连接):返回两个表中满足条件的交集。 LEFT JOIN(左外连接):返回左表的所有记录以及右表中匹配的记录。 RIGHT JOIN(右外连接):返回右表的所有记录以及左表中匹配的记录。 FULL JOIN(全外连接):返回两个表中所有记录,未匹配的部分用NULL填充。 CROSS JOIN(交叉连接):返回两个表...
order_number FROM users INNER JOIN orders ON users.id = orders.user_id; 左连接会返回左表中的所有记录以及与右表匹配的记录,如果右表中没有匹配的记录,则对应的列值为 NULL。例如: 代码语言:sql AI代码解释 SELECT users.username, orders.order_number FROM users LEFT JOIN orders ON users.id = ...
INSERT INTO users (username, password, email, age) VALUES ('Alice Smith', 'alicepass', 'alice@example.com', 30), ('Bob Johnson', 'bobpass', 'bob@example.com', 35); 复制 查询数据 查询数据是数据库操作中最常用的功能之一。使用 SELECT 语句从表中检索数据。例如,查询 users 表中的所有记录...
21.1 Join Types and Methods 连接是sql语言的一个关键特性,它们是sql语言灵活性的基础。行的集合(直接从表中检索或者作为其他操作的结果接收)总是成对进行连接。 有如下连接类型:Inner join,outer join,anti-join and semi join Inner joins:内连…阅读全文 赞同 添加评论 分享收藏 ...
The join condition specified withONcan also contain conditions that do not relate directly to the join. This can prove useful for some queries but needs to be thought out carefully. For example: test=>select*fromt1leftjoint2ont1.num=t2.numandt2.value='xxx'; ...
In the above example, the 'id' column appear only once, because this column is common in both the tables. Here, PostgreSQL implicitly does an INNER JOIN on that column.LEFT JOIN or LEFT OUTER JOINIn LEFT JOIN when joining table supplier with table orders PostgreSQL first does a "normal" ...
PostgreSQL 连接(JOIN) # CROSS JOIN :交叉连接- 数据大量冗余 - 笛卡尔积# INNER JOIN:内连接- 仅包含两个表都有的数据# LEFT OUTER JOIN:左外连接- 以左侧表为主 - 当左侧出现的数据,右侧未曾出现,则右侧空匹配# RIGHT OUTER JOIN:右外连接- 以右侧表为主 ...
在MySQL和PostgreSQL中,都可以使用JOIN、LEFT JOIN、RIGHT JOIN和INNER JOIN来进行不同类型的连接。虽然语法相似,但在实际应用中可能有一些细微的差别。例如: 代码语言:sql AI代码解释 -- MySQLSELECTa.*,b.*FROMtable_a aINNERJOINtable_b bONa.id=b.a_id;-- PostgreSQLSELECTa.*,b.*FROMtable_a aINNERJOIN...