decode function

--1, use month as conditional filter (to_char function and extract function)SELECT * from Test_date where To_char (DQSJ, ' mm ') like '%07% ';SELECT * from Test_date where extract (month from DQSJ) = 6;--2, get view nameSELECT * from User_views;--3,

Oracle broadly divides functions into single-line functions, aggregate functions, and analytic functions.Single-line functions are divided into character functions, date functions, conversion functions, numeric functions, general functions, decode

(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,

(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,

In the development of the report, many times will encounter row and column conversion operations, the developer for the SQL level row and column conversion operation has been not very understanding, today just time to make some simple summary. Here

We have to do not only write SQL, but also to write a good performance of SQL, the following for the author to learn, excerpts, and summarize some of the information to share with you!(1) Select the most efficient table name order (valid only in the

Oraclesql optimization of the statement : Select the most efficient table name order: the table with the lowest number of record bars should be selected as the base table! Because the Oracle parser is processed in a right-to-left

The first thing to figure out is the execution plan?An execution plan is a query scheme that the database makes based on the statistics of SQL statements and related tables, which are generated automatically by the query optimizer, such as an SQL

(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

(Transferred from http://blog.csdn.net/sforiz/article/details/5345359)We have to do not only write SQL, but also to write good performance of SQL statements.(1) Select the most efficient table name order (valid only in the rule-based optimizer):The

Warm tip: This article is from the Internet, I only do a little processing, not detailed research, only as a later unprepared for the need, if you like to enjoy the turn away.First, the question of the proposedIn the early stage of application

I've seen a private message recently. I asked some optimization questions for Oracle SQL, shared an article about SQL optimization, and later shared some more articles about SQL optimization.(1) Select the most efficient table name order (valid only

Very good SQL statement optimization 34 article1) 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

SQL Optimization Experience Summary 34 article we want to do not only write SQL, but also to write a good performance of SQL, the following for the author to learn, excerpts, and summarize some of the information to share with you! (1) Select the

To add a column:ALTER TABLE TableName add ColumnName datatype (not NULL); -------One thing to note is that when adding a column that is not empty, the table must be an empty table.To delete a column:ALTER TABLE tablename DROP column ColumnNameTo

One day in a technology group to see someone sent such a figure for help, a look at the problem is to examine the use of SQL row to columnI thought the first time I think of Oracle's decode function to write, but also think that the topic is not

(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,

1. The connection order in the WHERE clause:Oracle parses the WHERE clause in a bottom-up order.According to this principle, the connection between tables must be written before other where conditions, and those conditions that can filter out the

============ Recommended ============csdn:http://blog.csdn.net/e3002/article/details/1817941= = = How to optimize SQL statements = =(1) Select the most efficient table name order (valid only in the rule-based optimizer):    Oracle's parser processes

Tag: Equals line tab SQL statement HTTP return hive SQL developmentOriginal link: http://www.cnblogs.com/juddhu/archive/2012/03/07/2383101.htmlDecode function usage in OracleMeaning explanation:Decode (condition, value 1, return value 1, value 2,