how to write distinct query in sql

Label:IntroductionSee a popular blog today. NET Senior Engineer face questions of SQL, asked to find the highest score of each department, and by the department number, the student number in ascending order. This query is more complex, but also more typical, since the use of ORM, a long time did not write SQL statement

How to write better SQL queries: Ultimate Guide-Part 2: Ultimate SQL query In the previous article, we learned how to execute SQL queries and what to note when writing SQL query statem

Query Analyzer is 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 co

IntroductionSee a popular blog today. NET Senior Engineer face questions of SQL, asked to find the highest score of each department, and by the department number, the student number in ascending order. This query is more complex, but also more typical, since the use of ORM, a long time did not write SQL statements, so

Label: in the service, put the parameters in the HashMap listNewArraylist(); List.add ("X"); List.add ("Y"); List.add ("Z"); String s= "A"Date D=NewDate (); HashMapNewHashmap(); Param.put ("List", list); Param.put ("S", s); Param.put ("D", D); Xxxdao.queryxxx (param); In MyBatis's mapper, it reads:Select* from tab where Zi_duan1 = #{s} and zi_duan2 =#{d} and Zi_duan3 inSeparator= "," close= ")" >#{item} In the service, put the parameters into the HashMap list(); List.add ("x"); List.add ("Y");

Tags: query statement sql650) this.width=650; "Src=" http://images2017.cnblogs.com/blog/139239/201708/139239-20170829102801202-859313490. JPG "width=" 399 "height=" 257 "style=" border:0px; "/>Structured Query Language (SQL) is an indispensable skill in the data mining and analysis industry, and it is generally easier to learn this skill. For

OverviewHow do you write SQL query statements that are relatively high performance? Two methods: Create a reasonable index; write efficient SQL statementsFundamentals of IndexingThe index is divided into clustered and nonclustered indexes. A table can only create one cluster

Tags: SQL query statements650) this.width=650; "Src=" http://images2017.cnblogs.com/blog/139239/201709/139239-20170911112105313-661504674. JPG "width=" 423 "height=" 235 "style=" border:0px; "/>This time we learned the last article of how to write a better SQL query series.T

650) this.width=650; "Src=" http://images2017.cnblogs.com/blog/139239/201709/139239-20170911112105313-661504674. JPG "width=" 423 "height=" 235 "style=" border:0px; "/>This time we learned the last article of how to write a better SQL query series.Time complexity and large o symbolsThrough the first two articles, we have a certain understanding of the

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 Oracle parser processes the table names in the FROM clause in a right-to-left order, and the FROM clause is written in the final table (the u

the length of a little longer, here is not much to say. Finally make a summary, query optimization is the following methods: 1: Increase the index or rebuild the index. It is common to index fields in foreign keys, connection fields, sort fields, filter queries, or through Database Engine Tuning Advisor information. Sometimes when you create an index, you find that the query is executed in the same way as

fromPUB_CONSULT1) CLINICALTB onClinicaltb.consultid=Pub_consult1.consultid Left Join(Select distinctApplicationID,sum(Traniningnumber) asNum fromDbo. Review_aid_usetraining_recordwhereAidreferralid is NULL Group byApplicationID) tab ontab. ApplicationID=Pub_consult1.applicationidINNER JOIN(SelectCONSULTID,DBO.F_GETAIDNAMEBYCONSULT1 (Consultid) asAidname fromPUB_CONSULT1) Aidnametb onAidnametb.consultid=Pub_consult1.consultid Left OUTER JOINPub_user onPub_application.reviewuserid=Pub_user.user

follows:CREATE TABLESyslanguage (IdINT PRIMARY KEY, 中文版NVARCHAR( -), ChineseNVARCHAR( -), FrenchNVARCHAR( -))INSERT intoSyslanguageVALUES(1,'Hello','Hello','Empty')INSERT intoSyslanguageVALUES(2,' World','World','Empty')INSERT intoSyslanguageVALUES(3,' Book','Book','Empty')INSERT intoSyslanguageVALUES(4,'Open','Open','Empty')INSERT intoSyslanguageVALUES(5,'Save','Save','Empty')INSERT intoSyslanguageVALUES(6,'New','New','Empty')So, with system performance in mind, we may use stored procedu

pages to find the appropriate results, while the former only scans each row in the table.The second part of the tutorial is described here. There will be a final article on how to write a better SQL query series, so stay tuned.Original link: http://www.kdnuggets.com/2017/08/write-better-

( -), ChineseNVARCHAR( -), FrenchNVARCHAR( -))INSERT intoSyslanguageVALUES(1,'Hello','Hello','Empty')INSERT intoSyslanguageVALUES(2,' World','World','Empty')INSERT intoSyslanguageVALUES(3,' Book','Book','Empty')INSERT intoSyslanguageVALUES(4,'Open','Open','Empty')INSERT intoSyslanguageVALUES(5,'Save','Save','Empty')INSERT intoSyslanguageVALUES(6,'New','New','Empty')So, with system performance in mind, we may use stored procedures to reduce network traffic and improve response times. So, in

I believe that the brothers who have used hibernate will find that after the multi-Table complex query,Worried about how the returned results are assembled into a vo.. I keep worrying about it, but I am reading it.Hibernate TransformLater, I feel that this method is quite useful. For example, there are two tables, one is the user table with some user information, the other is the post posted by the user, and there is a foreign key for the user. We nee

Two Tables union query, sub-table FID has the same only fetch one, how to write SQL statements? This post was last created by Dfwye on 2012-11-09 19:45:23 Edit two table union query, the child table FID has the same only one, how to write

My SQL is very poor, half a day response to, was a colleague joke. Oh, ah ah. Must surpass him later!!Table ShopPk_shop PRIMARY KeyName Commodity Shop Pk_shop Name 001 Down 002 Coca - cola Bpm_ll_test2 PK_BPM_LL_TEST2 PRIMARY Key Sname Product Name 01 001 Select (select name from shop where shop s s.pk_shp

"1" cip_admin_domain (option field a)---> Inside configuration (Option field a) property, Defalut_value set initial value (such as: Create a new project, the project status after creation is "pending approval")Cip_admin_codes (option field a)Note: Two fields in the table, and, front page code "option" field--"must be consistent,"2" multi-conditional value function, in SQLSelectfield A, field B(CaseWhen (codes. Field 1 = ' option English alias 1 ') Then ' Chinese name 1 'When (codes. Field 2 = '

Tags: tar create done Project class User A mat statusReference: https://bbs.csdn.net/topics/330032307There is a dictionary table in the database, which contains the ID field and the corresponding name fields.In another record table, there is a corresponding ID for the dictionary table above, and there are multiple fields that contain the ID field. It needs to be identified and used by name.SELECTa.ID as 'numbering',' Story' as 'type', A.title as 'title', B.name as 'Affiliated Projects', A.proje