sql query tuning techniques in oracle

SQL connection query for Oracle databasesPrefaceIn reality, there is such a requirement that sometimes the data we need to query is in multiple tables, so how to query data from multiple tablesWhat about it? In this case, you need to use table connections to perform queries.

☆Retrieve all table names and column names of the databaseSelect name from sysobjects where xtype = 'U'Select name from syscolumns where id = (select max (id) from sysobjects where xtype = 'U' and name = 'table name ')☆Recursive Data QueryRecursive query of SqlServer2005 and Oracle in SQL statementsI used Oracle before

Tags: PID pool table mina ext execution SID proc App--Query for the slowest SQL SELECT * FROM (Select Parsing_user_id,executions,sortsCommand_type,disk_reads,sql_text from V$sqlarea ORDER BY disk_reads Desc) Where rownum --Query corresponding session Select SE. Sid,se. Serial#,pr. SPID,TEI Username,se. Status,se. TERMINAL,TEI Program,se. MODULE,TEI Sql_address,st

Different databases: oracle mysql SQL Server DB2 infomix sybase paging query statement, infomixsybase Paging query statements used in different databases: Current page: currentpagePage size: pagesize 1. Oracle Database Select * from (select A. *, rownum rn from (QUERY_

BackgroundWhen using Oracle or other databases, using the LIKE keyword for fuzzy query is commonly used by people, in the use of pure Chinese environment is very easy to use, there are some wildcards can be used, but in a pure English environment, the size of the need to accurately match the problem, the main reason is the problem of string FL like '%{0}% ' and Here like after is a string, so

ORACLE basic SQL statements-query, oraclesql statements 1. Common Query /* Query table data */Select * from STU /* Retrieve the first three rows of Data */Select * from stu where ROWNUM /* Fuzzy query */Select * from stu where s

This article provides a detailed analysis of the implementation of Oracle SQL statements for querying and deleting jobs, for more information about how to query and delete duplicate records, see SQL statement 1. For more information about duplicate records in a table, see select * frompeoplewherepeopleIdin (selectpeopl

PL/SQL single-row functions and group functions A function is a program with zero or multiple parameters and a return value. Oracle has a series of built-in functions in SQL, which can be called SQL or PL/SQL statements. functions are mainly divided into two categories:Singl

:A. Needs to be queried from the database: Totalrecords. "SELECT COUNT (*) from TableName"B. The most basic needs of user-provided: PageSize and Pagenow. (Personally think this is the premise of pagination algorithm)C. Derived from other variables: TotalPages, Beginrow and Endrow. (it needs to be calculated that Beginrow and endrow are required for paging queries, TotalPages is the information that the page needs to provide). Specific formula for calculation: Totalpages:if ((totalrecord

Tags: data SP problem BS database server SQL as installationWhen SQL Server accesses a database table in Oracle remotely:The remote syntax is typically: SELECT * from OpenQuery (Oracle linked server name, ' query statement ')Eg:select * from OPENQUERY (QTX, ' select * from s

Oracle processes query statements in three major stages: parse, execute, and fetch ). Oracle processes query statements in three major stages: parse, execute, and fetch ). Steps for Oracle to execute SQL

The paging query method for Oracle, SQL, and DB2 is different from that for paging query statements in Oracle and SQL, the following describes the differences between DB2 paging query a

For a while, I was confused about Oracle multi-table queries. The reason is that Oracle's own syntax is mixed with SQL's international standard syntax. ThisArticleIt is only suitable for Oracle cainiao, and old birds fly directly... Multi-Table connection type (SQL 1999 standard) •Cross joins •Natural joins •Using clause •Full (or two-sided) Outer joins

Many of my friends who use mysql limit for paging to oracle do not know how to write paging. In fact, oracle paging is similar to mssql paging. Next I will introduce oracle paging statements. Simplest use The Code is as follows: Copy code Select t2 .*From (select rownum r, t1. * from youtable t1 where rownum Where t2.r>? If the numb

Oracle Real-Time query resource consumption SQL 1. first, use the top command to view the pid Number with more resources in production. Note: For the oacle of the top Command user, follow the pid www.2cto.com 2. query the current time-consuming session ID, user name, And sqlID. Among them, the pid in top is the spid fi

A detailed explanation of the Double quotation marks required for table names and Field Names during oracle SQL statement Query As a beginner in oracle, I believe everyone will encounter this problem, It is clear that navicat created a table visually, but it cannot be found! Why? Select * from user; However, if we add

* fromEmpwhereEmpno not inch(SelectEmpno fromEmpwhereRowNumSize*(page- 1)) andRowNumsize; --sorting and then paging query --number of data after sorting (Efficiency row 2nd) Select * from(SelectRowNum RN, D.* from(Select * fromEmpOrder bySaldesc) d)whereRn> 5 andRn One; --Paging function: row_number function (1th efficiency row) SelectRow_number () Over(Order bySaldesc) RN, EMP.* fromEMP; --page Out Select * from(SelectRow_numbe

Page Size *From table1where id>(select Max (ID) from(Select Top ((page 1) * page size) ID from table1 ORDER by ID) as T)ORDER BY IDHow much of this method does not always have a big drop, the stamina is still very sufficient. Especially when the data volume is large, the execution speed of the method is not reduced at all.Using top requires that the primary key must be unique and cannot be a federated primary key. If it is a federated primary key, the query