SQL Server String Functions

ASCII (character_expression) returns the ASCII code value of the leftmost character
Char (integer_expression)

Unicode (ncharacter_expression) returns the integer of the first character of the input expression according to the definition of the Unicode standard.
Nchar (integer_expression)

Lower (character_expression) is returned with lowercase characters in the string
Upper (character_expression)

Ltrim (character_expression) truncates left English Spaces
Rtrim (character_expression)

Len (string_expression) returns the number of characters (not bytes), excluding trailing English spaces.
Left (character_expression, integer_expression) trailing spaces may also be returned
Right (character_expression, integer_expression)
The position of the first character of substring (expression, start, length) is 1

Charindex (expression1, expression2 [, start_location]) position of expression1 in expression2
Patindex (% pattern %, expression) pattern should have wildcards, like
Reverse (character_expression) reverse string
Replace (string_expression, string_expression2, string_expression3) Replace the second expression in the first expression with the third expression
Stuff (character_expression, start, length, character_expression) Delete the content of the first expression by START and length and insert the fourth expression at the start position

Replication (character_expression, integer_expression) Duplicate string
Space (integer_expression) Duplicate integer_expression Space

Soundex (character_expression) returns a specific string of four lengths Based on the string.
Difference (character_expression, character_expression) compares the sounex return values of two expressions with several different characters. The return value is [0-4].

STR (float_expression [, length [, decimal]) returns the string value converted from a number.
Quotename (character_string [, quote_character]) returns a unicode string with a separator