datepart sql oracle

SQL optimization should be adjusted from five aspects:1. Remove unnecessary full table scans for large tables2. cache full table scan for small tables3. Verify the use of optimized Indexes4. Verify the optimized Connection Technology5. minimize the Cost of the Execution Plan SQL statement:Is the only way to operate databases (data;70% ~ 90% of database resources; independent of the program design logic, com

oracle| data Advanced Data Migration A lot of time, to the heterogeneous database data migration or extraction, if the Oracle data extraction in SQL, through ODBC, OLE DB and other means, to extract data from the Oracle SQL, mostly through a transparent gateway to achieve.

The source of this article, in order to facilitate direct copy over. If there is infringement, please inform, thank youhttp://blog.csdn.net/chiclewu/article/details/14646687An Oracle 11g 64-bit version was installed in the virtual machine today, and when connected with PL/SQL developer, it was found that there was no database connection to TNS.It is considered that the PL/

Tags: oracle optimized SQL optimization Base Access tableMethods of accessing dataThere are two types of data in the Access table: 1, direct access to table 2, first access to the index, and then back to the table1, direct access to the table of two ways:①, full table scanFull-table scanning refers to when Oracle accesses the data of the target table, it starts s

Oracle SQL Execution flowchart _ SQL Execution Process 1. SQL statement execution steps:1) analyze the syntax and analyze whether the syntax of the statement complies with the specifications, to measure the meaning of each expression in the statement. 2) perform Semantic Analysis to check whether all database objects i

following method to implement the original statement: Select/* +Rule*/Y. deptno, Y. ename, Y. empno, Y. Job, X. sal_tot, X. comm_tot From (select empno, sum (sal_amt) sal_tot, sum (Comm) comm_tot From salary s Where S. deptno in (select deptno from employee like '2013 ') And S. sal_date between '20160301' and '20160301' Group by empno) x, employee y Where Y. empno = x. empno; Run the rule prompt to execute the SQL statement according to the index rul

page; pagenumber pages from the client; Total number of records in totalrecouds table select COUNT (*) from table name totalpages total pages totalpages= totalrecouds%pagesize==0?totalrecouds/pagesize:totalrecouds/pagesize+1 pages start position pages= pagesize* (pageNumber-1) sql statement: select * from table name limit pages, pageSize; mysql paging depends on the keyword limit it requires two parameters: start position and pagesize

Oracle SQL optimization rules: Use the in operator as few as possible. Basically, all in operators can be replaced by exists. The SQL statements written in are easier to write and understand, but the SQL statements written in always have low performance, the steps executed by Ora