sql query tuning techniques in oracle

cannot generate connection record (extra record) SelectE1.ename, E2.ename fromEMP E1 Left JoinEMP E2 on(E1.mgr=e2.empno); --full external link, the left and right side of the record can not generate connections to query out SelectENAME, Dname fromEMP E Full JoinDept D on(E.deptno=D.deptno); --From the connection, the same table will be different aliases, and then as two tables to use. The self-connection can be connected either inside or outside. Se

This article summarizes the Oracle implementation of page query SQL syntax, collation for everyone for your reference, details are as follows: 1. No order by sort of the wording. (Highest efficiency) After testing, this method costs the lowest, only nested one layer, the fastest! Even if the amount of data query is l

Use this SQL statement Select*FromTree View the raw data as follows: The following figure shows the result of a tree query (including the fields ROOT, LEVEL, IS_LEAF, and PATH ): Execute the following SQL statement: SelectConnect_by_root (child_col) root,Level, Decode (connect_by_isleaf, 0,'No', 1,'Yes') Is_leaf, sys_connect_by_path (child_col,'/') Path F

| | '. ' | | a.index_name| | ' rebuild nologging online; 'From Dba_indexes Awhere A.table_name= ' WWFF 'and a.statusand a.partitionedSteps to read 3Hint forced to walk the index (only used to view the hint state, whether the query changes, the application can not be changed)Select/*+index (WWFF idx$$_wwff_jgsj) */* from WWFFwhere Jgsj>=to_date (' 2014-10-26 00:00:00 ', ' yyyy-mm-dd HH24:Mi:SS ')and Sjzt=1 and Fjbj=3 and Fjr=1 and rownum Takes 0.03 s

Tags: function implementation style IMA database data result ref using colorIn an Oracle database, you can merge fields using the wm_concat (column) functionThe Oracle Wm_concat (column) function allows us to use it frequently, and below teaches you how to use the Oracle Wm_concat (column) function to implement a field merge if you have an

Tags: using data SP C size r database SQL BSPaged query statements that are used in different databases:Current page: CurrentPagePage Size: pagesize1. Oracle DatabaseSELECT * FROM (select A.*,rownum rn from (query_sql) A) where Rn Note: query_sql is a query SQL statement.OrS

Oracle Spatial spatial data SQL query related instances -- Select dlbm, dlmc, trim (zldwdm) as zldwdm_1 from gzdt where nvl (zldwdm, 'T') = 'T' or zldwdm = '';Update gzdt set zldwdm = '000000' where nvl (zldwdm, 'T') = 'T' or zldwdm = '';Commit;Delete from gzdt where zldwdm like '20160301'Commit;// Obtain the space areaUpdate gzdt set mj = MDSYS. sdo_geom.sdo_are

Like fuzzy query for oracle, mysql, db2, and SQL server in Mybatis, mybatisdb2 Different database languages: SQL server, Oracle, mysql, db2'' There are too many database system types. To put it simply, ACESS is suitable for small websites. asp and MYSQL are recommended for

Original address: http://www.cnblogs.com/ginponson/p/5746435.htmlAssuming that this is page pageno, there are pagesize records per page, and now the student table is queried using MySQL, Oracle, and SQL Server paging.Paging Query for 1.MysqlSELECT * from Student -1* pagesize,pagesize;Understanding: (Limit n,m) + starts from the nth line to fetch M Records, n f

How can I view the current number of connections in Oracle? You only need to use the following SQL statement to query it. Select * from V $ session where username is not null Select username, count (username) from V $ session where username is not null group by username # view the number of connections of different users Select count (*) from V $ session #

Oracle spatial Query SQL query all the elements of a certain distance from a certain point (that is, the general query) SQL: www.2cto.com select t. objectid, t. comp_type, t. datatype, t. comp_name, t. health_lic, t. shape. SDO_PO

Query the method for binding variable values in Oracle SQL statements, oraclesql Alter session set nls_date_format = 'yyyy-mm-dd, hh24: mi: ss'; set linesize 400col SQL _Id format a20col name format a20col datatype_string format a14col value_string format a20select SQL _id,

Oracle merge query transaction SQL function knowledge learning. For more information, see Oracle merge query transaction SQL function knowledge learning. For more information, see Table que