oracle query optimization tool

Basic query optimization and subquery Optimization in Oracle databases 1. Reasonably sort query Conditions Oracle uses the bottom-up sequence to parse WHERE data. From the perspective of performance

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1. Reasonable sorting of query conditions Oracle uses a bottom-up sequence to parse where writes, and from an optimized performance perspective, it is recommended that the conditions that filter out a large number of record rows be written at the end of the WHERE clause, and the table The connection conditions between are placed before other where clauses, that is, the easy to determine the conditions of

Tags: sel div weight span subquery query lag around 11gEnvironment: Oracle 11g The existing A and B tables are associated with the A01 field, and the data in table A is not available in B. SQL as follows Select Count (1 from (select A.*, (selectCount(1) from where b.a01=as fromwhere flag=0 Because flag is a virtual field, the index causes the SQL to execute particularly slowly, and the total number of 3

Some Oracle database query optimization suggestions are comprehensive, oracle Database 1. To optimize the query, try to avoid full table scanning. First, consider creating an index on the columns involved in where and order.2. Try to avoid null value determination on the fie

,'YYYYMMDD') Rangebetween thePreceding Currentrow)End asf70115_70011, Case whenA.c_date>To_char (sysdate-3,'YYYYMMDD') Then sum(VALUEF1) Over(Partition byA.code,a. Year Order byTo_date (A.c_date,'YYYYMMDD') Rangebetween thePreceding Currentrow)End asf70104_70011, Case whenA.c_date>To_char (sysdate-3,'YYYYMMDD') Then sum(VALUEF6) Over(Partition byA.code,a. Year Order byTo_date (A.c_date,'YYYYMMDD') Rangebetween thePreceding Currentrow)End asf70126_70011, Case whenA.c

Tags: field tno div sort between records job employee EXPI. View employee employee Information (Query the department number ==10 and sort in ascending order by the entry time. The second is replaced by numbers)Second, sort by multiple fields (Dmpno,deptno,sal,ename,job)Third, according to the sub-string sort (there is a quick check method, is in accordance with the customer phone number tail number order records, so that the

can be followed by parameters: All or cpu,block io,page faults and so on.You can also query directly in the Information_schema.profiling database table:Select State,sum (Duration) as Total_r,round (100*sum (Duration)/(select SUM (duration) from Information_ schema.profiling where [email protected]_id), 2) as Pct_r,count (*) as Calls,sum (duration)/count (*) as "R/call" from inform ation_schema.profiling where [email protected]_id GROUP BY state ORDE

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The basic task of a database is to store and manage data, and the only database feature that an end-user can see is its performance: how quickly the database processes the results of a given query, and returns the results to the tools and applications used by the user. From the application examples of most systems, query operations occupy the largest proportion in various database operations, access to news

1, for columns like the state, not many, you can add bitmap index, for unique columns, add a unique index, the rest of the creation of normal indexes.2. Try not to use a query such as SELECT * To specify the columns you want to query.3. Use hits Select/*+index (index name) index (index name) */supply_id from css_supply where ...4. Redefine table tables as partitioned tables, use hash partitions or range par

Oracle Query optimization(1) Select the most efficient table name order (only valid in the rule-based optimizer): The Oracle parser processes the table name from the FROM clause in a right-to-left order, and the last table written in the FROM clause (base table driving tables) is processed first. In cases where the FRO

Oracle's optimizer has been improved by actual application feedback. Oracle's optimizer contains 4 major components (these sections are discussed in detail in the following sections): SQL statement conversion: In Query optimization Oracle uses a series of sophisticated techniques to transform SQL statements. The purpose of this step in

the first SQL statement.12: Impact of query orderThe list order in the table following FROM will affect SQL Execution performance.In this case, ORACLE links the tables in the order they appear,As a result, data that consumes a lot of server resources is generated when the table order is incorrect. (Note: If statistical analysis is performed on a table,ORACLE aut

that of the first SQL statement.12: Impact of query orderThe list order in the table following FROM will affect SQL Execution performance.In this case, ORACLE links the tables in the order they appear,As a result, data that consumes a lot of server resources is generated when the table order is incorrect. (Note: If statistical analysis is performed on a table,ORACLE