db2 subquery

1. query the employee information with higher salaries than scott. Step 1: query the employee's salary selectsalfromempwhereenameSCOTT; Step 2: query the employee information with higher salaries than scott. select * fromempwheresal3000; conclusion: subquery essence: nesting of multiple select statements 2: Knowledge body of subquery 1. query the employee information with higher salaries than scott. Step 1:

Subquery 1 (subquery in WHERE), where in subquerySubquery A subquery is a compilation of complex queries by embedding several small queries with different functions in a complete query statement, to help readers better understand the concept of subqueries. Subquery return resultsData types that can be returned by subqu

Label:1. What are sub-queries?When a query is a condition of another query, it is called a subquery.2. What are the benefits of sub-queries?Subqueries can use a few simple commands to construct powerful composite commands.Well, now let's learn the subquery together.Sub-query of model 3.whereGive it a definition: the Where sub-query is the result of the inner query as the condition of the outer query.Now, le

Tags: sts post ecshop direct 4 line query optimization exist 0.00 explain In -type sub-query leads to traps: (Sweep less rows, not temporary tables, do not sort files quickly) title: In the Ecshop Mall table, query 6th items, (note, number 6th is a large column) the most intuitive: MySQL> SelectGoods_id,cat_id,goods_name fromGoodswherecat_idinch(Selectcat_id fromCategorywhereparent_id=6); Misunderstanding: Give us the feeling is, first found in the inner layer of column 6th sub-column, such as 7

Label:One, the basic type of sub -Query multiple rows subquery (1) Use the in operator for multi-line subqueries. (Summary: Multiple rows of subqueries available after the in operator) For example: Query the highest-paid employee information for each position. Sql>select ename, Job, Sal from EMP where sal in (select Max (SAL) from EMP Group by Job);--Single row subquery Or Sql>select ename, Job, Sal fr

Tutorial on column-subquery and row-subquery operations in MySQL, MySQL column subquery and use of the in, ANY, SOME, and ALL operatorsMySQL column subqueryA column subquery is a result set returned by a subquery that contains N rows and one column. This result is usually re

Oracle _ advanced subquery, oracle _ advanced subqueryZookeeper Oracle _ advanced subquery ① SubqueryA subquery is another SELECT statement nested in an SQL statement.Subquery (internal query) is executed before the master query is executed.Main query (external query) uses the subquery results ② Multi-column subqueryCo

Oracle single-row subquery and multi-row subquery instances 1. the query is divided into primary queries and subqueries; 2. The records returned are divided into single-row subqueries and multi-row subqueries. single-row subqueries use single-row comparison operators = connections. multi-row subqueries use multi-row comparison operators in connections; 3. The content of the

Correlated subquery and non-correlated subquery: the query name nested in other queries. A subquery is also called an internal query, while an external query (also called a primary query) contains the subquery statement ). All subqueries can be divided into two types: correlated subqueries and non-correlated subqueries

Subquery: queries nested in other queries.A subquery is also called an internal query, while an external query (also called a primary query) contains the subquery statement ).All subqueries can be divided into two types: correlated subqueries and non-correlated subqueries.1> non-correlated subqueries are subqueries that are independent from external queries. subq

Database subquery, database subquerySubquery A select statement also contains another select statement, in which the select statement is called a subquery. Subqueries can be divided into the following categories based on the position where select appears: From subquery Where subquery Exists

Oracle subquery, oracle subquery Subquery: contains another query within a query. Common subquery -- Query the information of all employees whose salaries are higher than 7654. select * from emp e where e. sal> (select sal from emp where empno = 7654); -- query the information of all employees who have the same job

Subquery 4 (use subquery in select clause), select clause Example 1,Query the number, name, location, department count, and average salary of each department. SELECT d.deptno,d.dname,d.loc, (SELECT COUNT(empno) FROM emp WHERE emp.deptno=d.deptno GROUP BY deptno) con, (SELECT AVG(sal) FROM emp WHERE emp.deptno=d.deptno GROUP BY deptno) avgsalFROM dept d WITH clause Example 2,Use the with clause to define

Error code: 1242 Subquery returns more than 1 row, 1242 subquery1. Error description 1 queries executed, 0 success, 1 errors, 0 warnings query: SELECT t. id, DATE_FORMAT (t. statisTime, '% Y-% m-% d % H: % I: % s') statisTime, (SELECT 'id' FROM t_truck_info WHERE id = t. plateId... error code: 1242 Subquery returns more than 1 row execution time: 0.009 sec Transfer Time: 0.002 sec total time: 0.012 sec2. C

---average wageSELECT AVG(SAL) fromEMP;-----------greater than average salarySELECTE.ename,e.job,e.sal fromEMP EWHEREE.sal>(SELECT AVG(SAL) fromEMP)----------e leader Number =m employee number--EMP Employee table, Dept Department tableSELECTE.ename Employee name, e.job employee position, e.sal employee salary, M.ename leadership name, m.job leadership position, D.dname department name fromEMP e,emp m,dept DWHEREE.sal>(SELECT AVG(SAL) fromEMP) andE.mgr=M.empno (+) andE.deptno=D.deptno-----------P

Query paging filtering spring's stuff is too cumbersome to write. The simple thing to do is to query the Sysuer table based on the type parameter, and if type exists, filter by type, otherwise query all Sysuer (not including patient). The service layer paged query is called in the following places: @Override public pageThen the conditional implementation of paged query is implemented in the Sysuserspecification Topredicate method. public class Sysuserspecification implements specificatio

A subquery (subquery) refers to a SELECT clause that appears within other SQL statements.For example:SELECT * from t1 where col1= (select col2 from T2);where select * from T1, called Outer query/outer Statement (outer query)Select col2 from T2, called subquery (subquery)The subquer