how to tune sql query

When converting Oracle queries to SQL queries, you need to pay attention to a lot of issues. The following gives you a detailed analysis of the number trade-offs in converting Oracle queries to SQL queries for your reference. Number trade-offs Oracle Database has a TRUNC function, which returns n digits of the m-bit decimal number. If m is omitted, n is 0 digits. The m value can be negative, indicating th

Mysqli compared to MySQL has a lot of advantages, recommend that you use, if you do not know, you can view the basics of MySQL tutorial:MYSQLI Connection Database and mysqli preprocessing prepare used. Not only that, mysqli is more support for multiple query features, look at the following section of PHP code: Copy Code code as follows: $mysqli = new Mysqli ("localhost", "root", "" "," new "); $mysqli->

=name; This. Minage =Minage; This. MaxAge =MaxAge; } PublicString GetName () {returnname; } Public voidsetName (String name) { This. Name =name; } Public intGetminage () {returnMinage; } Public voidSetminage (intminage) { This. Minage =Minage; } Public intGetmaxage () {returnMaxAge; } Public voidSetmaxage (intMaxAge) { This. MaxAge =MaxAge; } }configuration file for 4.sql queries Selectusermapper.xmlnamesp

Paging query and SQL paging QueryIn fact, there is no difference between paging query and other queries. The main difference is that the query statement is not available, and paging query may be a little more troublesome. Next we will explain how to implement our paging

the equals sign are unknown, the result is true or false,sql cannot give a definite result, so the result of the query is null. Therefore, it is necessary to explicitly use a null value test that is null or a negative form field is not NULL to detect null values. The following is the truth-table of And,or,not in SQL. Table 1 Truth-Tables of and

Alibaba Cloud SQL Intelligent Query analyzer, a database query and analysis management tool developed by delphi. To facilitate your work, you can use a database query and analysis management tool developed by delphi to share with you the following features: 1. Due to the use of ADO connections, it theoretically sup

, Administrativename,administrativeremark from Cet_administrativeoption (maxrecursion 0); GOOracle:1. From the root node to the child node:SELECT Administrativeid,administrativepid,administrativename,administrativeremark from Tadministrative START with Administrativepid is a NULL CONNECT by PRIOR Administrativeid=administrativepid;2. Query from child nodes to the root node:SELECT Administrativeid,administrativepid,administrativename,administrativerema

The SQL statement used to query multiple fields, query multiple tables, and delete duplicate records. SQL repeat record Query 1. Search for redundant duplicate records in the Table. duplicate records are determined based on a single field (peopleId ). select * from people wh

Hibernate native SQL query, Hibernate native SQL Recently, a more complex query was made, and the basic query of hibernate could not meet the requirements. Therefore, we had to use the native SQL

SQL subquery, multi-Table query, and joint Query Subquery, multi-Table query, and joint QueryThese three concepts are interpreted slightly differently in different SQL versions, roughly as follows: JoinYou can check related SQL

I wrote a half-day SQL statement in the query analyzer and forgot to save it ~ What should I do if I want to retrieve an SQL statement that has been executed for a certain period of time? I wrote a half-day SQL statement in the query analyzer and forgot to save it ~ What sho

(1) retrieve all rows and columns from the table Problem View All data in a table. Solution Use the SELECT statement for the table and the special character "*". select * from emp Discussion The "*" symbol in SQL has special significance. You can use this function to return each column in a specified table. Because there is no WHERE clause, each row in the table is returned. Another alternative is to list each column separately. select empno,ename,job

Tags: Scroll method prepare win section data body multiple ICAThe most obvious feature of SQL differs from other programming languages is the order in which the code is processed. In a large number programming language, code is processed in encoded order, but in the SQL language, the first processed clause is the FROM clause, although the SELECT statement first appears, but is almost always finally processe

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 why is this? To understand why, you need to

into' Student 'VALUES('8','Lee 48','123','male',' +','Jingan, Shanghai city'); INSERT into' Student 'VALUES('9','Zhang 39','111','male',' +','Shiyan, Hubei province'); INSERT into' Student 'VALUES('Ten','Lee 40','123','male',' +','Jingan, Shanghai city'); I. Querying 5~10 data MySQL Paging query: SELECT * FROM student limit 5, 10; Oracle Paging query: SELECT * FROM (select *,rownum rn from student) wh

SQL query begins with a specified character SQL query statementLike a lot of time we need to be in the MySQL tutorial, MSSQL to query eligible data, today I came across a query with "Deng" all the conditions of the beginning of th

longitude and latitude two columns in the data table to optimize the speed at which the where statement executes.The final SQL statement is as follows 1 $sql=‘select * from users_location where 2 latitude >‘.$lat.‘-1and 3 latitude ‘.$lat.‘+1and 4 longitude >‘.$lon.‘-1and

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**********

subqueries, multiple table queries, federated queriesThese three concepts are interpreted slightly differently in different versions of SQL, roughly as follows: Join connectionCan look at the relevant SQL information, or buy a book of SQL 1, such as: SELECT * from TAB1 where ID in (SELECT id form tab2 where ...)The query