nested subquery

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

Label:One, sub-query definition　　Defined: Subqueries allow a query to be nested within another query. subqueries, also called internal queries, are called external queries, as opposed to internal queries, which contain internal queries. A subquery can contain any clauses that a normal select can include, such as: Distinct, group BY, order by, limit, join, and union, and so on, but the corresponding external

---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

Technical preparationThe database version is SQL Server2008R2 and is analyzed using Microsoft's simpler case Library (Northwind.1. Independent subqueryThe so-called independent subquery method means that the subquery is irrelevant to the primary query. The advantage of this method is that the subquery does not depend on the external query, so it can be evalua

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

Oracle Database Advanced subquery ① subquery A subquery is another SELECT statement nested in an SQL statement subquery (internal query) that executes the primary query (external Oracle Database Advanced subquery ①

|+----+-------------+------------------+------+---------------+-------+---------+-------+------+--------------------------+1 row in set (0.00 sec) No problem. You only need to scan several rows of data. The index takes effect. Query it to see: mysql> select number_id from abc_number_phone where phone = '82306839';+-----------+| number_id |+-----------+| 8585 || 10720 || 148644 || 151307 || 170691 || 221897 |+-----------+6 rows in set (0.00 sec) Directly store the data obtained from the

query), and creates a nonclustered index for those rows. This allows you to use the lookup function of the index to output only those rows that satisfy the SEEK: () predicate.If you re-orbit the operator (for example, by Nested Loops operator) but do not require any rebinding, the spool data will be used without rescanning the input.Similar to the index offline, there is a similar operator: The table is offline, its function is similar, the table is

The Oracle subquery is detailed. The subquery types are divided into single-row subqueries and multi-row subqueries Based on the query results (nested query results, The Oracle subquery is detailed. The subquery types are divided into single-row subqueries and multi-row subq

Multi-table join: You can specify multiple tables directly after the FROM clause. in semantics, you can retrieve data FROM the Descartes of these tables. You can use the WHERE clause to set filtering conditions. The SQL Server link syntax is as follows: SELECT table_name.column_name, table_name.column_name ,...... FROM {table_name, table_name ,......} WHERE table_name.column_name join_operator table_name.column_name In this syntax, the FROM clause lists all the table names used during the conne