JDBC SQL转义语法是什么意思？请解释一下

转义语法使您能够使用特定于数据库的功能，这些功能无法通过使用标准的JDBC方法和属性来实现。

一般的SQL转义语法格式如下：

{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 format

{d 'yyyy-mm-dd'}

Where yyyy = year, mm = month; dd = date. Using this syntax {d '2009-09-03'} is March 9, 2009.

Example

//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);

escape关键字

此关键字用于标识在LIKE子句中使用的转义字符。当使用SQL通配符%，该字符可以匹配零个或多个字符时非常有用。例如−

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

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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 −

{fn length('Hello World')}

这返回11，字符串'Hello World'的长度。调用关键字

此关键字用于调用存储过程。例如，对于需要IN参数的存储过程，请使用以下语法−

{call my_procedure(?)};

对于需要一个IN参数并返回一个OUT参数的存储过程，请使用以下语法 −

{? = call my_procedure(?)};

oj关键字

该关键字用于表示外连接。语法如下−

{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);