SqlServer STUFF function:
STUFF（<character_expression>，<开始>，<长度>，<character_expression>）
The <character_expression> parameter is the given string data, which can be a constant, variable or column of character or binary data.
The <start> parameter is an integer value that specifies the position to start deleting and inserting. It can be of type BIGINT. If the <start> or <length> parameter is a negative number, a NULL string is returned. If the <start> parameter is longer than the first <character_expression>, a NULL string is returned.
The <length> parameter can be of type BIGINT, which is an integer that specifies the number of characters to be deleted. If <length> is longer than the first <character_expression>, the deletion occurs to the last character in the last <character_expression>
DECLARE @Time VARCHAR(10)
SET @Time = ‘1030’
SELECT STUFF(@Time, 3, 0, ‘:’) AS [HH:MM]
Output: 10:30
The string we give is @Time, which is 1030. We start from the third position and delete the length as 0. At this time, we insert a colon before 3, and the result is 10:30 as shown in the figure above.
DECLARE @CreditCardNumber VARCHAR(20)
SET @CreditCardNumber = ‘370200199408103544’
SELECT STUFF(@CreditCardNumber, LEN(@CreditCardNumber) -3, 4,
‘XXXX’) AS [Output]
Output: 37020019940810XXXX
As above, we pass the ID card through STUFF and replace the last four digits with XXXX. The above is the most basic usage of STUFF
mysql INSERT函数：
mysql> SELECT INSERT('abcdef', 2, 3, 'ijklmn');
+----------------------------------+
| INSERT('abcdef', 2, 3, 'ijklmn') |
+----------------------------------+
| aijklmnef |
+----------------------------------+