how to write distinct query in sql

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How to write query statements in ThinkPHP

How to write query statements in ThinkPHP? Similar to QQ, a user information table allows users to have friends. how can I query User friend information and display it on the page? Thank you, GGMM !,, At least you should give the relevant table structure. what is the relationship with the framework? you design the relevant database and search the data accordingly

Improve SQL query efficiency (SQL Optimization) (reproduced)

Tags: type error associated recommendation management will rom Ora no(Transferred from http://blog.csdn.net/sforiz/article/details/5345359) We have to do not only write SQL, but also to write good performance of SQL statements.(1) Select the most efficient table name order (valid only in the rule-based optimizer):The O

Thinkphp four-level correlation query How to write, online etc.

Thinkphp Four-level association query how to write? Relationship: A in B's aid,b in C's bid,c in D's CID, how to associate it? A-->b-->c-->d M ("D")->jion ("A on B.aid=a.id)->jion (" B on C.bid=b.id)->jion (' C on D.cid=c.id ') This is not the case Reply to discussion (solution) Your expression was wrongly written.->join (' A on B.aid=a.id ')->join ("B-c.bid=b.id")->join ("C on D.cid=c.id") Join ()

T-SQL query-understanding the lock in SQL Server

shows the DMV. It is worth noting that the SYS. dm_tran_locks DMV shows the database lock at the query time point and does not contain any history lock records. It can be understood as the snapshot when the database is locked at the query time. SYS. dm_tran_locks contains two types of information: Information about the resource where the lock is located starting with resource, and information about the a

How to write the simplest query result statement

I don't have PHP, but now there's only PHP space, Want a function, very simple one, Two columns (A B) in the data table Implementation: I enter a value in the text box, in the database query a column of the value of the B column corresponding to the value and return to the page. The amount ... Can a great God help write a more complete sentence? That includes the database Connection statements section.

Python read text data write to database and query optimization

(ip_list)): sql_list.append (Sql_tmp.format (' t ' +str (i)) %ip_list[i]) sql= ' unionall '. Join (Sql_liST) t0=time.time () #forrowin Db.query (SQL): #print (Row) dict ( Zip (ip_list,db.query (SQL))) t1=time.time () for ipinip_list: ret=db.get (' SELECT *FROM ' Test '. Ipdatawhere%s>=startiporderbystartipdesc limit1 ', ip) startip,endip= Ret.get (' StartIP '),

An SQL query method learned by a Q & A (Multiple-to-multiple-link query interview questions)

Q A location: http://space.cnblogs.com/q/20546/q A: I have asked more questions about the relationship: 5 [resolved issues] Browse: 52 times 00 Student table T1 Stu_id Stu_name 1 Zhang San 2 Li Si 3 Wang Wu Course list T2 Co_id Co_name 1 Java 2 C # 3 C 4 C ++ 5 Javascript Link Table T3 Stu_id Co_id 1 1 1 4 2 1

An interesting SQL query (query 7 consecutive days to log in)

An interesting SQL queryA friend has such a SQL query requirement:There is a login table (Tmp_test) that contains the user ID (UID) and logon time (Login_time). The table structure is as follows:*************************** 1. Row***************************Field:uidtype:int(Ten) unsignedNull: NOKey: MULDefault:NULLExtra:*************************** 2. Row**********

SQL =null Query results and is null to query the result description

Tags: that is greater than stronggrouplov in insert get address When we want to query all result sets in SQL for which a column value is NULL, the query condition should write like thisSELECT * FROM table where field is nullInstead, use the SELECT * from table where field = NULL to not find the correct result. Then

Ask the great God, so write, PHP query is executed two times?

Prepare ("Delete from Naszt where 1=1 and id=?"); if ($del->execute (Array ($id))) {echo "";} Else{echo "; }}?> Prepare ("SELECT * from Naszt"); $selectSpecialContent->execute ();? > Topic name type of topic Publication Time Publish IP Operation Fetch ()) {?> "> "> View "> Modify ">the > Delete Ask the great G

Mysql-how should I write a MYSQL statement to directly query data in two tables?

The two tables have the same names: c_biao_1 and c_biao2 $ SQL quot; select * fromc_biao_1whereuid $ uidandjs0orderbyaddtimedesc quot ;; how should I write these two tables in one statement? In addition, the fields in both tables are the same !~ I mean, I want to use a statement to query the mysql data from two tables. Both data tables are the same.The tw

MS SQL Server Query optimization method (1) There are many reasons for the slow query speed, common as follows:

difference between commit and Rollback Rollback: Roll back all things. Commit: Commit the current thing. There is no need to write things in dynamic SQL, if you want to write please write in the outside such as: Begin TRAN EXEC (@s) commit trans or write dynamic

Spring Boot learning experience using jparepository annotation custom SQL query database multi-table query

Tags: _id repos query Statement automatic learning experience query logs SQL definitionFirst, in the @entity annotated class to write a good foreign key relationship.This @ManyToOne annotation can establish a foreign key relationship, not in their own silly write a private i

For developers to write Maxcompute sql more cool, DataWorks enhanced SQL Editor features

complete the code folding. 7, intelligent editor Lenovo Speed improvement The new version of the editor, not only support 2.0, in the Lenovo speed also increased by 40%, to achieve faster, more accurate. 8, code search support More ways The new version supports more flexible query methods such as case, regular expressions, etc., and users can turn on the code retrieval function via Ctrl+f. -------------------------------------------------------

SQL Server Fourth Lesson: View Query method, paging Query method

Label: CREATE VIEW View_1--Create a new view name as--functions for building viewsSelectStudent.sno,sname,cno,degree fromStudent join score on student.sno=Score.sno GoSelect* fromView_1wheresno='1' Select* from (SelectStudent.sno,sname,cno,degree fromStudent join score on STUDENT.SNO=SCORE.SNO) asTable2 wheresno='101'--define as a temporary table with AS and then query the results from the table. is also a sub-qu

How can I write this query statement correctly?

How should I write this query statement correctly? $ sns = $ db-> field ('distinct (dname) 'AS 'd _ name', 'Count (dname) 'as')-> where (array ('lid' => intval ($ _ GET ['id']), 'islottery' => 1 )) -> GROUP ('dname')-> order ('tjs desc')-> select (); Reply to discussion (solution) Table ??,????, Check? ? Result.What do you want to provide? To know? How ?? Ah. DISTINCT is a keyword, not a function.

Kettle implements dynamic SQL query and kettle implements dynamic SQL

Kettle implements dynamic SQL query and kettle implements dynamic SQLDynamic SQL query in kettle In ETL projects, some SQL statements, such as data query, are usually executed based on the input parameters at run time. This artic

How to write high-performance SQL statements

considered to be two different SQL statements, must be parsed two times. Generate 2 execution plans. So as a programmer, you should ensure that the same query statements everywhere are consistent, one more space is not!3. Do not write SQL statements too complexI often see a SQL

MS SQL Basics Tutorial: SQL Query Analyzer

19.3.1 SQL Query Analyzer Introduction SQL Query Analyzer is a graphical management tool that is used to write, test Transact-SQL statements, and batch processing. System administrators and developers can learn how to improve per

C # write WPF program, SQLSever2008 prompt to insert data successfully, but cannot query data

1. Prompt for storage success, but no data in the database.When you write a WPF program in C # today, you insert data into the database SQL server2008.The program prompt succeeds, but opens the database but has no value;The query found that the data was stored in the database under the default path.Database default Path@ "Data source=.; attachdbfilename=| Datadir

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