SELECT column_name FROM table_name WHERE column_name NOT IN (SELECT column_name FROM another_table) 注意,"NOT IN"操作符在使用时需要确保子查询的结果集不包含NULL值,否则可能导致不符合预期的结果。 "NOT EXISTS": "NOT EXISTS"操作符用于判断子查询的结果集
TheNOT INoperator in SQL is used to fetch all the records that aren’t present based on a particular field. We can use this operator to select records from one table that aren’t present in another table: SELECT * FROM Course c WHERE c.id NOT IN ( SELECT r.course_id FROM Registratio...
SELECTcolumn_name(s)FROMtable_nameWHEREEXISTS(SELECT1FROManother_tableWHEREcondition); 1. 2. 3. 4. 5. 6. 7. SELECT 1:在 EXISTS 的子查询中,通常使用SELECT 1或其他任何常量,因为 EXISTS 只关心是否返回了行,而不关心实际返回了什么值。 WHERE condition:这是你的连接条件,它定义了主查询和子查询之间...
SELECTcolumn(列名), another_column, … FROMmytable(表名) 2、条件查询-SELECT WHERE 2.1 适用于数字类型的属性 为了更精确的查询出特定数据:SELECT查询的WHERE子句. 一个查询的WHERE子句用来描述哪些行应该进入结果,具体就是通过 condition条件 限定这些行的属性满足某些具体条件 1 2 3 4 5 6 7 8 条件查询语...
SELECTstor_id,qtyFROM(SELECTstor_id,qtyFROMsalesWHEREqty>50)AStemp_table;2、UNION UNION运算符从...
In SQL, the SELECT INTO statement is used to copy data from one table to another. Example -- copy all the contents of a table to a new table SELECT * INTO CustomersCopy FROM Customers; Here, the SQL command copies all data from the Customers table to the new CustomersCopy table. ...
代码:SELECT `nickname`,`email`FROM `testtable`WHERE `name`='张三' (一) 选择列表 选择列表(select_list)指出所查询列,它可以是一组列名列表、星号、表达式、变量(包括局部变量和全局变量)等构成。 1、选择所有列 例如,下面语句显示testtable表中所有列的数据: ...
select 12, 10; select * from random.organization_dimension; alter table random.organization_dimension add column organization_name varchar(20); update random.organization_dimension set organization_name = concat('Firm',organization_key); -- For given Firm ID = 7 as in the example. ...
SELECT L.lea_id, L.f_name, R.mod_id, R.mode FROM Learners L LEFT JOIN Reg R ON L.lea_id = R.lea_id; Output: Explanation: Here, this LEFT JOIN extracts all learners who are in the Learners table and their registration details from the Reg table. If a learner has not registered...
1CREATE DATABASE [IF NOT EXISTS] db_name; 举例: Plain Text 复制 1新建数据库 db_test 2CREATE DATABASE db_test; Create Table 该语句用于创建表(table) 语法: Plain Text 复制 1CREATE [EXTERNAL] TABLE [IF NOT EXISTS] [database.]table_name 2 (column_definition[, column_definition, ......