decode function

Reprinted: http://blog.csdn.net/jallin2001/archive/2009/11/13/4808618.aspx   The regular expression character set is often used to extract or exclude Chinese characters from a string. However, this is very troublesome and the effect is not very

34 PL/SQL Optimizations   We should not only write SQL statements, but also write SQL statements with excellent performance. The following sections will help the author learn, extract, and summarize some materials to share with you!(1)

[Optimization] 34 SQL Optimizations We must not only write SQL statements, but also write SQL statements with excellent performance. The following section describes how to learn, extract, and summarizeShare the information with you!(1) select the

Oracle SQL Performance Optimization: 1. select an appropriate Oracle optimizerThere are three optimizer types in Oracle A. Rule (Rule-based) B. Cost (cost-based) C. Choose (selectivity) Set the default optimizer. You can declare the optimizer_mode

Encoding of characters in Python. During encoding and conversion, we must be clear about the encoding method of the string we read, or the encoding method of the string we want to decode. Then we can use decode to decode the string, decodes a

We should not only write SQL statements, but also write SQL statements with excellent performance. The following sections will help the author learn, extract, and summarize some materials to share with you!(1) select the most efficient table name

These are a combination of online materials for your reference. Welcome to add ~ 1. Select the most efficient table name sequence (only valid in the rule-based Optimizer) First, set the rule optimizer and use the statement:Alter system set optimizer_

1. addslashesAddslashes escapes special characters in SQL statements, including ('), ("), (), (NUL) four characters, which are used when the DBMS does not have its own escape function, but if the DBMS has its own escape function, it is recommended

We must not only write SQL statements, but also write SQL statements with excellent performance. (1) select the most efficient table name sequence (only valid in the rule-based Optimizer ): The Oracle parser processes the table names in the from

Seven common Oracle functions and seven oracle Functions 1. decode Function Select id, NAME, DECODE (LEVER, 1, 'Professor ', 2, 'associate Professor', 3, 'mentor ', 'lecturer') POSITION, (select classnum from class t where t. NUM = S. NUM) num from

First look at the table content Select name, pass from t1; 2. Method 1: Use the decode Function Select name, decode (pass, 'passs111', 'pass1', 'pass222', 'pass1', '', 'Password') from t1; Note: If you do not list the possible conditions in the

ArticleSource: http://topic.csdn.net/u/20080808/14/dfc973e7-fcf2-4526-9de1-fa5efc148f5c.html We should not only write SQL statements, but also write SQL statements with excellent performance. The following sections will help the author learn,

1) Row-to-column Conversion Table Structure: Student Create TableStudent (User_name Varchar2(20), CourseVarchar2(20), ScoreFloat) Initialize data: Insert Into Student ( User_name , Course, score) Values (' Zhangyue ' , ' Enlish ' , 85

(1) simple integration with no associated database access:If you have several simple database query statements, you can integrate them into a single query (even if there is no relationship between them)(2) Delete duplicate records:The most efficient

(1) Select the most efficient table name sequence (valid only in the rule-based Optimizer ):The Oracle parser processes the table names in the from clause in the order from right to left. The table written in the from clause (basic table driving

We should not only write SQL statements, but also write SQL statements with excellent performance. The following sections will help the author learn, extract, and summarize some materials to share with you! (1) select the most efficient table name

34 SQL Optimizations We should not only write SQL statements, but also write SQL statements with excellent performance. The following sections will help the author learn, extract, and summarize some materials to share with you! (1) select the

From: http://www.iteye.com/topic/508161 Recently, javaeye found that many comrades know little about SQL optimization. Recently, I have summarized several articles for reference only. However, a few of them may depend on the situation, most of

// It's really boring. It's a strange idea. I want to re-use PHP to implement some encapsulated functions in PHP,// The following code mainly implements some string processing functions in PHP, and implements some PHP// None, but the same function

(1) simple integration with no associated database access:If you have several simple database query statements, you can integrate them into a single query (even if there is no relationship between them) (2) Delete duplicate records: The most