nested subquery

The value of the query condition comes from another query. For example, sqlserver SQL: Select * from products where categoryid = (select top 1 categoryid from categories where categoryname = 'produce ') The implementation code of this SQL statement is as follows: DbSession.Default.From Compare the SQL statements generated by the component Text: SELECT * FROM [Products] WHERE [Products].[CategoryID] = ( SELECT TOP 1 [Categories].[CategoryID] FROM [Categories] WHERE [Categories].[CategoryName] = @

Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->Create table tb1 (id int identity (1, 1), name varchar (10), remark varchar (50) default ''); Create table tb2 (xid int identity (1, 1), name varchar (10 )); Insert into tb1 (name)Select 'A'Union all select 'B'Union all select 'C'Insert into tb2 (name) select 'x' Select * from tb1 where id in (select id from tb2)Select * from tb1 where id in (select xid from tb2) Drop table tb1Drop table tb2; The r

Mysql exists subquery bitsCN.com Mysql exists subquery Subqueries can be divided into: from where and exists subqueries Category table: [SQL] Mysql> select * from category; + ---- + --------- + | Id | c_name | + ---- + --------- + | 1 | ios | | 2 | android | | 3 | sb | + ---- + --------- + 3 rows in set Item table: [SQL] Mysql> select * from goods; + ---- + --------- + -------- + ------- + ----- + | I

Original Sub-query SELECT COUNT (*) as Tp_count from Sdb_b2c_orders WHERE pay_status= ' 1 ' and createtime>1413533130 and Area_code in (1030,1 031,1032,1033) and member_id in (select member_id from Sdb_invite_invite where in_member_id=14273 or in_member_id=13742 or in_member_id=14299) LIMIT 1 Execution results are22 Use a connection query instead of the subquery above SELECT COUNT (*) as Tp_count from Sdb_b2c_orders as Bo INNER joins

There are two tables, A and B. Aid scriptid taskid yearID 1 5 3 1 2 5 4 1 3 5 5 1 4 6 3 1 5 6 4 1 6 7 3 2 7 7 5 2 8 8 2 2 9 8 6 2 Table B is as follows:Bid aid11 112 213 314 415 516 617 718 819 9 Obtain the maximum value of yearID = 1, scriptid = 5, and taskid not greater than 4 in table. Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/--> Select Scriptid, Max (Taskid) As Taskid From A Where Ybid = 1 And Scripti

The value of a query condition comes from another query. Like SQL Server sql: SELECT * from the products where categoryid= (select top 1 CategoryID from categories where categoryname= ' produce ') The implementation code for this SQL is as follows: DbSession.Default.From 　　　　　　　　 .Where(Products._.CategoryID 　　　　　　　　 .SubQueryEqual(DbSession.Default.From 　　　　　　　　 .ToList(); Compare the SQL generated by the component Text: SELECT　*　FROM　[Products] WHERE　[Products].[CategoryID]　=　(　SELECT　TO

, the corresponding data is displayed, if not the corresponding two parties can be empty--full join is mainly used in statisticsSELECT * from the staff s full join Department d on d.id = s.department_id;3. Sub-query:--In a subquery in Oracle, ORDER by is not ordered, and all oder by sorts are placed in the final query result--Information on teachers older than Zhangsan--Information for teachers older than the average age-Employee information under the

Recently learning Oracle, want to improve the efficiency and legibility of the written statement, today's note is about the subquery factor words such a thingA factorial query may not necessarily improve efficiency, but it can improve the readability of the program significantly The result of the--with statement with the Sales_c (select Sales,e_no,e_name from Emplyee) SELECT * from sales_c;--query is (select Sales,e_no,e_na Me from Emplyee) The

Tags: course ons stack mysql ber color div for LIS Watch_course_sql="""SelectDate_format (From_unixtime (a.createtime/ +) ,'%%y-%%m-%%d%%t') Regtime, A.username fromBskuser awhereA.usernameinch (Selectusername frombskchapterlistwhereLessonid= (SelectID fromBsklesson aWHEREA.lessonname like\'%s\') ) Limit%D - """ %(Coursename, page* -) the coursename from the front desk should be kanji But if the error comes when the background will be incorrect ' u'subquer

table, if you want to use a simple grouping is not possible, the above has been explained, and you can not guarantee that there will be more than the same results.Method One: First use the group to query out the class and the results of the maximum results as a new table, and the original table to jointly query out the corresponding student information.Method Two: If the best results have only one word of the special column, it is possible to sort the result set by class and score before groupi

'. ' St_stock_m 'WHERE(' ma '. ' St_stock_m '. ' Goods_no '='1230480') and (CACHE>(' ma '. ' m '. ' Cell_no ')=' ma '. ' st_stock_m '. ' Cell_no ')))) and(' ma '. ' loc '. ' Cell_no ')=' ma '. ' m '. ' Cell_no ')) Execution plan In fact, the subquery returns no more than 3 result sets, usually we think that the internal will be based on the use of the result set to check, the efficiency will be very fast, but it is not Thought the internal operati

Assume that the table my_tbl contains three fields A, B, and C. Now we need to query the minimum value of Column B under each different value of column A in the table. For example, the table record is: A B C 1 3 'cd' 2 3 'nhd' 1 5 'bg' 2 6 'cds' 1 7 'kiy' 3 7 'Password' 3 8 'ndf' Expected result: A B C 1 3 'cd' 2 3 'nhd' 3 7 'Password' (1) One method is to first find the minimum value of B under each a value, and then query all records that meet the requir

Label:Nested queries mean that one query statement (select-from-where) query block can be nested within another query block's WHERE clause, called a nested query. Where the outer query is also called the parent query, the main query. An inner query is also called a subquery, from a query. Nested queries work by process

When mysqlin subqueries are simply optimized to a large number, do not use in nested subqueries. The performance is poor and it is easy to get stuck .? The simple adjustment method is as follows: selectuid, nick_namefromuc_userswhereuidin (selectfidfromuc_followwhereuid # uid #)? It can be split into: 1. selectfidfromuc_followwher When a large number of mysql in subqueries are simply optimized, do not use in nest