MySQL Exception Handling

1. Definitions

　　And java abnormal, are used to define the problems encountered in the process and the corresponding processing mode.

2, and custom exception handling

　　1, custom exception statement

　　　　DECLARE condition_name CONDITION FOR condition_value；

　　　　condition_name: from the name of their own, the best known name meaning see.

　　　　condition_value: may be SQLSTATE [VALUE] sqlstate_value may be mysql_error_value.

　　　　　　sqlstate_value error code is a string of 5.

　　　　　　mysql_error_value error code is a numeric type.

　　2, a custom exception handler

　　　　DECLARE handler_type HANDLER FOR condition_value sp_statement;

　　　　handler_type: There are three values

　　　　　　CONTINUE: An error was encountered no treatment over the code after the error continues.

　　　　　　EXIT: Exit immediately when an error is encountered, is no longer operating after execution.

　　　　　　UNDO: to withdraw before the operation has been executed after an error is encountered, MySQL does not support this operation.

　　　　condition_value: Error name: The following values

　　　　　　condition_name: take the definition of abnormal name

　　　　　　mysql_error_value: error code type value

　　　　　　SQLWARNING: shorthand for all SQLSTATE codes for the beginning of the 01's　　　　

　　　　　　NOT FOUND: shorthand for all SQLSTATE codes for the beginning of the 01's

　　　　　　SQLEXCEPTION: Shorthand SQLSTATE codes other than the SQLWARNING and NOT FOUND.

　　　　sp_statement: treatment after abnormal.

　　3, the example shows

　　　　Create the following table, the u_id as the primary key, and insert the following data:

　　　　Create a stored procedure called insert_user of:

BEGIN
    set @x = 1;
    insert into users values(3,'zhaoliu',26);
    set @x = 2;
    insert into users values(4,'zhouqi',27);
    set @x = 3;
END

 

　　　　By using user variables @x to see whether the code is running, call a stored procedure

call insert_user();

 

　　　　The following error occurred

Where the number 1062 is mysql_error_code. Corresponding sqlstate_value is '23000', the specific correspondence table can be seen in a corresponding manner.

Check the value of @x

select @x;

 

We can see u_id = 3 of this statement appeared abnormal.

Next we add exception handling:

The BEGIN 
    #Routine body goes here Wallpaper ... 
    # 1: Direct Exception handling 
    # DECLARE Exit 1062 the FOR HANDLER SET X1 = @. 4; 
    # way: first custom exception, then the exception handling using
     the DECLARE ERROR1 CONDITION for  1062 ;
     DECLARE  Exit HANDLER the FOR  1062  SET  @ X1  =  . 4 ; - handler_type first use herein Exit
     SET  @x  =  . 1 ;
     INSERT  INTO Users values ( . 3 , ' zhaoliu ' , 26 is );
     SET  @x  =  2;
    insert into users values(4,'zhouqi',27);
    set @x = 3;
END

 

 

Here To test the effect of exception handling we set the @ x1 is set to 4.

Call the stored procedure again would not be incorrect report

select @x,@x1;

 

Query User Variables

It found that when an exception occurs, the program will execute exception handling and exits the process.

The process handler_type changed to continue, repeat the procedure, it will not go wrong.

Query User Variables

After the discovery of the code for the following exception handling, we will continue to run

Queries users table

Abnormal insert statement is not executed, but the statement was no exception occurs behind the execution.