how to tune sql query in oracle

oracle| Performance | execution The cost of using the Oracle execution planning mechanism to improve query performance the time of the new SQL statement is the most important part of the Oracle SQL statement execution time. But by

Oracle learning notes 4 SQL commands (2): SQL operation language category, oracle learning notes SQL is classified into the following language categories1. Data Definition Language (DDL)Create, Alter, Drop 2. Data manipulation language (DML)Insert, Select, Delete, Update 3.

ORACLE query optimization and gather_plan_statistics hint, oracledbmsgather Query Optimization Methods and gather_plan_statistics hint:After 10 Gb, we can use the gather_plan_statistics prompt to learn more about SQL Execution statistics. The usage is as follows: If the statistics_level parameter is set to ALL, or the

(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 underlying table, driving tables) will be processed first, and in the case where the FROM clause contains more than one table, you must select the table with the fewest number of record bars as the underlying table. If you

The growth of SQL Server Cognition 1. I don't have to graduate or work for a long time. I only know the relationship between SQL and SQL Server Oracle and MySql. I usually think that SQL is SQL Server.2. after several years of wor

Distributed | data | database / * t-SQL code to implement distributed query of heterogeneous database using MS exec sp_addlinkedserver ' ms_sql ', ', ' SQLOLEDB ', ' 172.18.9.20 'exec sp_addlinkedsrvlogin ' Ms_sql ', ' false ', NULL, ' Sa ', ' capec '/* Create a remote link for SQL Server to SQL Server database * * ex

be processed first. When the FROM clause contains multiple tables, you must select a table with the least number of records as the base table. If there are more than three tables for join query, You need to select the cross table (interp table) as the basic table, the cross table is the table referenced by other tables. (2) join order in the WHERE clause.: ORACLE uses the bottom-up sequence to parse the WH

" for the [Html] The program is the same as above.Pay attention to the following issues when calling stored procedures:To use stored procedures in Hibernate, you must follow some rules. stored procedures that do not follow these rules will be unavailable. if you still want to use them, you must pass the session. connection () to execute them. these rules apply to different databases. because database providers have different stored procedure syntax and semantics.You cannot use setFirstResult ()/

Oracle paging query tutorial and oracle paging tutorial SELECT * FROM (select rownum as rowno, t .* FROM table t where rownum Page with order by statement: SELECT * FROM (select rownum as rowno, r .* FROM (SELECT * FROM table t Order by t. element asc ) R Where ROWNUM ) Table_alias WHERE table_alias.rowno> (page-1) * size; The upper limit condition

1: When multiple table associations are used, the multiple where statement minimizes the result set of a single table, uses aggregate functions to summarize the result set, and then associates with other tables to minimize the amount of result set data 2: You should consider the possibility of using a right connection when you are associating two tables. To improve query speed3: Use where instead of having , where is used to filter rows, and having is

exist. Although it is not specified when you create a table, some internal fields added to Oracle for maintenance are, these fields can be used as common files.The most familiar pseudo-column is rowid, which is equivalent to a pointer pointing to the position of the record on the disk. Ora_rowscn is newly added to Oracle 10 Gb. It is regarded as the SCN of the last modified record. The flashback version

"annual Salary"From EMP ORDER by 3 DESC;SELECT ename,job,sal from emp ORDER by Job,sal DESC;SELECT ename,job,sal from emp ORDER by Empno;Modify Default display widthSET line[size] {80|n}SET Line 100L display the SQL statement in the buffer you just enteredN Text modified section of error'/' (run) commandSAVEGET@ or Start command when the specified script file contents are loaded into the SQL buffer to runS

Pq_distribute hints are often used to improve the performance of connection operations between partitioned tables in the Data Warehouse. The Pq_distribute hint allows you to determine how table data rows participating in a connection are allocated between production and consumption parallel query service processes. Pq_distribute prompt accepts three parameters: table name, outer allocation, and internal allocation.When parallel

Oracle cold, stay at home and read the "Mastering Oracle SQL" 2nd, found that Oracle's function is still very strong, there are 200 optical functions, hsql is difficult to match. The next stubborn, it seems either to risk using Hibernate3.0 SQL mapping function, or to run the JDBC assembly VO. 1. Report Totals dedicate

SmallProgramGrowth of SQL Server Cognition 1. I don't have to graduate or work for a long time. I only know the relationship between SQL and SQL Server Oracle and MySQL. I usually think that SQL is SQL Server. 2. after several

The previous examples demonstrate the performance improvement caused by the standard writing of paging query statements. Here, we will briefly describe when paging query statements cannot improve performance. The paging query statement can return results quickly because it aims to return the first result as quickly as possible. If there are 20 records on each

I. Operator Optimization 1. In Operator SQL statements written in are easy to write and understand, which is suitable for modern software development. However, SQL statements using in always have low performance. The following differences exist between SQL statements using in and SQL statements without in:

the rownum=2 results. Since rownum are all starting from 1, but more than 1 of the natural numbers in rownum do equal to the judgment is considered false condition, so can not find rownum = N (n>1 natural number).Sql> Select Rownum,id,name from student where rownum=1; (You can use a limit to return the number of records to ensure no errors, such as: implicit cursors)Sql> Select Rownum,id,name from student

the table (Sp_spaceuse)3. Upgrading hardware4, according to the query criteria, index, optimize the index, optimize access, limit the amount of data in the result set. Note the fill factor is appropriate (preferably using the default value of 0). The index should be as small as possible, using a Lie Jian index with a small number of bytes (refer to the creation of the index), do not Jianjian a single index on a5, improve speed;6, expand server memory

How to deal with the high cpu usage of oracle, this article will introduce the high CPU usage of the oracle process, You Need To Know More friends can refer How to deal with the high cpu usage of oracle, this article will introduce the high CPU usage of the oracle process, You Need To Know More friends can refer How t