JDBC SQL轉義語法是什麼意思？請解釋一下

轉義語法可讓您使用特定於資料庫的功能，這些功能無法透過使用標準的JDBC方法和屬性來實現。

一般的SQL轉義語法格式如下：

{keyword 'parameters'}

Following are various escape syntaxes in JDBC:

d, t, ts Keywords: They help identify date, time, and timestamp literals. As you know, no two DBMSs represent time and date the same way. This escape syntax tells the driver to render the date or time in the target database's for| yyyy = year, mm = month; dd = date. Using this syntax {d '2009-09-03'} is March 9, 2009.

Example

{d 'yyyy-mm-dd'}

escape關鍵字

#escape關鍵字

此關鍵字用於標識在LIKE子句中使用的轉義字元。當使用SQL通配符%，該字元可以匹配零個或多個字元時非常有用。例如−

//Create a Statement object
stmt = conn.createStatement();
//Insert data ==> ID, First Name, Last Name, DOB
String sql="INSERT INTO STUDENTS VALUES" + "(100,'Zara','Ali', {d '2001-12-16'})";
stmt.executeUpdate(sql);

If you use the backslash character (\) as the escape character, you also have to use two backslash characters in your Java String literal, because the backslash is also a Javascape character.

##fn Keyword

This keyword represents scalar functions used in a DBMS. For example, you can use SQL function

length

to get the length of a string −##

String sql = "SELECT symbol FROM MathSymbols WHERE symbol LIKE '\%' {escape '\'}";
stmt.execute(sql);

ee

{fn length('Hello World')}

#這回傳11，字串'Hello World'的長度。呼叫關鍵字

此關鍵字用於呼叫預存程序。例如，對於需要IN參數的預存程序，請使用下列語法−

{call my_procedure(?)};

對於需要一個IN參數並傳回OUT參數的預存程序，請使用下列語法−

{? = call my_procedure(?)};

oj關鍵字

該關鍵字用於表示外連接。語法如下−

{oj outer-join}

Where outer-join = table {LEFT|RIGHT|FULL} OUTERJOIN {table | outer-join} on search-condition.

String sql = "SELECT Employees FROM {oj ThisTable RIGHT OUTER JOIN ThatTable on id = '100'}";
stmt.execute(sql);

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