decode function

Meaning explanation: Decode (condition, value 1, return value 1, value 2, return value 2,... Value N, return value N, default value) The meaning of the function is as follows:IF condition = value 1 THENreturn (translation value 1)elsif condition =

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The following are the referenced contents: Really boring, whim, want to put some of the PHP inside the package has been provided to reuse PHP implementation again, So there is the following code mainly implemented in PHP part of the string

1. addslashesAddslashes escapes the special characters in the SQL statement, including ('), ("), (), (NUL) four characters, this function is used when the DBMS does not have its own escape function, but if the DBMS has its own escape function, then

(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 Right-to-left order, the last table (driving table), which is written in the FROM clause, is

Really boring, whim, want to put some of the PHP inside the package has been provided to reuse PHP implementation again, So there is the following code mainly implemented in PHP part of the string processing functions, while implementing a number of

The full execution order of the SELECT statement:The full execution order of the SQL SELECT statement:1. The FROM clause assembles data from different data sources; 2. The WHERE clause filters the record rows based on the specified criteria, 3, the

http://www.cnblogs.com/llrr/p/6655977.html (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

Oracle SQL Performance Optimization(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

SQL Optimization Tips1. 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

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

The Decode function is similar to a series of nested IF-THEN-ELSE statementsSelect decode (sign (variable 1-variable 2), 1, variable 1, variable 2) from dual; --Take a smaller valueThe sign () function returns 0, 1, 1, depending on whether a value

First, the question of the proposedIn the early stage of application system development, due to less development database data, the query SQL statement, complex view of the writing of the performance of the SQL statement is not good or bad, but if

(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,

 Single-line function①. Character functionsLOWER (x): Converts each word in X to lowercaseUPPER (x): Converts each word in X to uppercaseInitcap (x): Converts the first letter of each word in X to uppercaseCONCAT (x, y): Used to add y to X, with |

Equivalent if statementWhen the decode function compares 1 parametersSELECT Id,decode (inparam, ' becomparedparam ', ' value 1 ', ' Value 2 ') name from bank#如果第一个参数inParam = = ' Becomparedparam ', the name given by select is displayed as a value of

We have to do not only writeSQL, but also to write a good performanceSQLStatement.(1) Select the most efficient table nameOrder(Valid only in rule-based optimizer):Oracle's parser follows right-to-leftOrderThe table name in the FROM clause is

A common method to improve the efficiency of SQL query(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

Database Summary Language classification Detailed description 1. Data query Statements Select 2. Data manipulation statements (DML) Insert;Update;Delete; 3. Database definition