subquery example

do with this case. Now I want to replace them. My project has two tables: 1: Movie table, which contains detailed information about movies. Field Description: resource_volumecountIt refers to the total number of sets of a movie. This field is of the int type. Other fields that have little to do with this case are omitted. 2: Movie File Table:Tb_resource_primarvideo It refers to the number of actually existing sets of specific movies in the movie table. For

Subquery of the front-end learning database and the sub-learning database* Directory [1] defines [2] comparison operator [3] modifier keyword [4] [NOT] IN [5] to store the query result IN front When querying a database, subqueries are often required when the query conditions are complex. Subquery indicates the SELECT clause in other SQL statements. This topic describes subqueries in detail. Definition

Tags: structural elective course use name csdn and attribute contentContent from online:53090467The data of the main query is placed in the subquery for conditional validation, depending on the validation result (TRUE or FALSE) to determine whether the data results of the main query are retained.Here's an example of three tablesLet's start with the 3 datasheets that are used:Student Data Sheet:

Hello everyone, I encountered the following problem in the project: the example of using the combined primary key when the hibernate ing table is as follows: Product table: Item, the code for the primary key as the Union primary key ItemId is as follows: publicclassItemId {@ columnLongitemId; @ columnLonguserId;} @ Table (...) publicclassItem {@ Id Hello everyone, I encountered the following problem in the project: the

A nested subquery is an independent query that is not related to an external query. A subquery is executed only once, then execute the external query. The external query uses the subquery results during execution.The following is an example of a nested subquery:SelectEname, SalFrom EMPWhere SAL>(Select AVG (SAL) from E

is, a required statement can be solved at one time. If it is written from the inside out, you can check the Sales. SalesOrderDetail table and match the number of products (ProductNumber) value in the LIKE statement. You can connect these rows to the Sales. SalesOrderHeader table to obtain the Sales staff IDs (SalesPersonIDs ). Then, use SalesPersonID to connect to the SalesPersonID table. Finally, use ContactID to connect to the Person. Contact table. The Code is as follows: USE AdventureWorks;

--View other employees who have a higher salary than all 20 departmentsSELECT Ename,sal,deptno from emp WHERE deptno = 20;Select Ename,sal,deptno from emp where Sal>all (select Sal from emp where Deptno =20);exists function, when a subquery can return at least one record, then the expression returns True, the following example shows: View the employeeThe DepartmentSelect Deptno,dname from Dept D where EXIST

column subquery by combining a relative comparison operator. They test whether the comparison value matches all or part of the values returned by the subquery. For example, if the compare value is less than or equal to each value returned by the subquery, select STU_ID from GRADE where STU_SCORE As long as the st

comparison value matches all or part of the values returned by the subquery. For example, if the compare value is less than or equal to each value returned by the subquery, select STU_ID from GRADE where STU_SCORE As long as the student ID is greater than any of the above, it is displayed: select * from STUDENT where STU_ID >= any (select STU_ID from GR

of employeesFrom:s_empconditions: salary of salary > Chang EmployeesSelect Id,last_nameFrom S_empWhere salary >?Phase objectives: salary of Chang employeesFrom : s_empcondition: last_name = ' Chang ';Select SalaryFrom S_empwhere last_name = ' Chang ';Combination:3. Check the ID and name of all employees whose employees pay less than the average wageFor example: Find and The ID and last_name of the employee of Smith's same departmentMulti-valued

Basic knowledge1, associated subqueries and unrelated subqueries In a unassociated subquery, an internal query executes only once and returns its value to an external query, and the external query uses the value returned to it by the internal query in its processing. In the associated subquery, the internal query is executed once for each row of data returned by the external query. In addition, the informa

Label:Source: Why not a subquery in SQL Server is not recommendedIn SQL Server, subqueries can be divided into correlated subqueries and unrelated subqueries, but not-in clauses are common for unrelated subqueries, but the not-in clause leads to the following two types of problems: Inaccurate results Poor query performance Let's take a look at why we try not to use the NOT in clause. The problem of inaccurate resultsIn SQL Server,

| +------+--------+------+------+------+-----------+--------------+ 1 row in Set (0.00 sec) mysql> Example: Querying employee and Department tables using an inner join and displaying query results in ascending order of the age field mysql> mysql> Select Num,name,employee.d_id,age,sex,d_name,function-From employee,department where employee.d_id=department.d_id , order by age ASC; +------+--------+------+------+------+-----------+-------

I. Defining what a subquery is When a query is a condition of another query, it is called a subqueryYou can add a subquery anywhere in the SQL. two. When to use subqueries Use it when the problem cannot be solved in one step. For example: query whose salary is higher than SCOTT's high select ename from the emp where sal > (select sal from emp where ename = ' SCO

sets are called sub-queries. There are two types of sub-queries: One is to return only a single-valued subquery, at which point it can be used where a single value can be used, when a subquery can be considered a function that has a return value; Another is a subquery that returns a column of values, at which point the s