SQLite中的表達式

SQLite中的表達式

在SELECT的基本完整形式中，咱們會看到幾乎是全部的子句都會使用到表達式。如下是SQLite支持的表達式類型。

expr binary-op expr |                                                                                                                //二元運算符

expr [NOT] like-op expr [ESCAPE expr] |                                                                    //LIKE運算符，匹配模式的一種

unary-op expr |                                                                                                                 //一元運算符

( expr ) |                                                                                                                             //括號

column-name |                                                                                                                          //列名

table-name . column-name |                                                                                        //表名.列名

database-name . table-name . column-name |                                                                  //數據庫名.表名.列名

literal-value |                                                                                                                     //字面量

parameter |                                                                                                                       //差數形式

function-name ( expr-list | * ) |                                                                                       //函數

expr ISNULL |                                                                                                                   //處理NULL值

expr NOTNULL |                                                                                                              //非空

expr [NOT] BETWEEN expr AND expr |                                                                      //範圍

expr [NOT] IN ( value-list ) |                                                                                            //範圍

expr [NOT] IN ( select-statement ) |                                                                              //範圍

expr [NOT] IN [database-name .] table-name |                                                          //範圍

[EXISTS] ( select-statement ) |                                                                                       //存在

CASE [expr] ( WHEN expr THEN expr )+ [ELSE expr] END |                                  //條件結果

CAST ( expr AS type )                                                                                                     //轉換

本節將講解這些表達式中最爲經常使用的幾種，如運算符、NULL的運算、參數形式、匹配模式、內建函數、條件結果等內容。