You select data from one table, which is joined to another table that you can also select from. This way, you can get the data you need from any table in the database, as long as you join it in your query. If yo
If you delete a table that doesn’t exist, you’ll get an error. The IF EXISTS clause conditionally deletes the table if it already exists. When SQL Server drops a table, it also removes all data, triggers, restrictions, and permissions from that table. ...
FROM join_table join_type join_table [ON (join_condition)] 其中join_table指出参与连接操作的表名,连接可以对同一个表操作,也可以对多表操作,对同一 个表操作的连接又称做自连接。 join_type 指出连接类型,可分为三种:内连接、外连接和交叉连接。内连接(INNER JOIN)使用比 较运算符进行表间某(些)列数据...
用INNERJOIN连接表的语法 SELECTcolumn, another_table_column, … FROMmytable (主表) INNERJOINanother_table (要连接的表) ONmytable.id = another_table.id (想象一下刚才讲的主键连接,两个相同的连成1条) WHEREcondition(s) ORDERBYcolumn, …ASC/DESC LIMIT num_limit OFFSET num_offset;<br><br>##...
We can UPDATE a table with data from any other table in SQL. Let us consider the following two tables. CREATE TABLE student_old ( student_id INT ,
We can join multiple tables in the DELETE statement, just like in the SELECT statement. DELETE data from a table by joining with another table in SQL Let us consider the below tables. CREATETABLEorders(order_idINTPRIMARYKEY,customer_nameVARCHAR(100),order_dateDATETIME,total_ordersINT);INSERT...
A self join is a regular join, but the table is joined with itself. Self Join Syntax SELECTcolumn_name(s) FROMtable1 T1, table1 T2 WHEREcondition; T1andT2are different table aliases for the same table. Demo Database In this tutorial we will use the well-known Northwind sample database...
FROM <table_name> LEFT OUTER JOIN <table_name> ON <join_conditions> SQL OUTER JOIN Example The following example JOINs the region and branch tables on the region_nbr column. Here are the contents of the tables: Table: REGION region_nbr region_name 100 East Region 200 Central Region ...
database_name target_table 所在数据库的名称。 schema_name target_table 所属架构的名称。 target_table <table_source>中的数据行根据<clause_search_condition>进行匹配的表或视图。target_table是由 MERGE 语句的 WHEN 子句指定的任何插入、更新或删除操作的目标。
左连接(LEFT JOIN) 左连接返回左表中所有行,以及右表中与左表中匹配行的交集。如果右表中没有匹配的行,结果集中右表的列将包含 NULL 值。 基本语法如下: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 SELECT column1, column2, ... FROM table1 LEFT JOIN table2 ON table1.column = table2.col...