MySQL stored procedure cursor traversal result set

Create stored procedure ：​​​​​​​

# Determine whether the stored procedure exists , There are deletions 
DROP PROCEDURE IF EXISTS toCard;
CREATE DEFINER=`root`@`%` PROCEDURE `toCard`()
BEGIN
	# Declaration end identifier 
	DECLARE end_flag int DEFAULT 0;
	# Variable 
	DECLARE userId,cardThird bigint;
	DECLARE cardHex,leftCard,rightCard,ecardNum VARCHAR(10);
	
	# declare cursor  user_curosr, take sql The result set is assigned to the cursor 
	DECLARE user_curosr CURSOR FOR SELECT id,ecardNumThird FROM u_user WHERE ecardNumThird IS NOT NULL AND ecardNumThird!='';
	
	# Set termination ID 
	DECLARE CONTINUE HANDLER FOR NOT FOUND SET end_flag=1;
	
	# Open cursor 
	OPEN user_curosr;
	
	# Traversal cursor 
	REPEAT
	
		# Get the current cursor pointer record , Get the value and assign it to the custom variable , notes ： The variable name should not be the same as sql The returned column names are the same , The order of variables should be the same as sql The result columns are in the same order 
		FETCH user_curosr INTO userId,cardThird;
			SET cardHex=CONV(LEFT(cardThird, 8), 10, 16);
			SET leftCard= CONV(LEFT(LPAD(cardHex,8,0) , 4), 16, 10);
			SET rightCard= CONV(RIGHT(LPAD(cardHex,8,0) , 4), 16, 10);	
			SET ecardNum=LPAD(CONCAT(leftCard,rightCard),8,0);
			# Output results 
			#SELECT userId,cardThird,cardHex,leftCard,rightCard,ecardNum;
			# Use the obtained value to operate the database 
			UPDATE u_user SET ecardNum=ecardNum WHERE id=userId;
	
	#  according to  end_flag  Judge whether it is over 
	UNTIL end_flag END REPEAT;
	
	# Close cursor 
	close user_curosr;

END

Execute stored procedures ：

call toCard();

It contains wiegand26 Card number conversion agreement