SQL Server knowledge Point record sharing

Introduction to Knowledge points

• Two-way search: Here is not a concept, directly say its role
• ISNULL () function: Determine if the function has a value, if the variable is not assigned to the given value, the following example is if the @TOTALCOUNT variable is null then the assignment is an empty string, if we will @TOTALCOUNT The variable is given an initial value then the print is 0 otherwise it is 1, you can copy run a bit to know

  DECLARE @TOTALCOUNT INT

  IF ISNULL(@TOTALCOUNT,") ="

  PRINT ' 1 '

  ELSE PRINT ' 0 '

• LTRIM () Remove the left space of the variable
• RTRIM () Remove the right space of the variable
• REPLACE () swap character The first argument is a variable name, the second is the source substitution character, and the third is the string to replace
• CHARINDEX () returns the starting position of the specified expression in the string, CHARINDEX(', ', @UserName) >0, checking if a comma exists in the UserName field
• UPPER() converts a string to uppercase format
• SUBSTRING() intercepts a string of a specified length The first argument is a variable name or a table field name, the second argument is the starting index, and the third is the terminating index
• Cast(@PageSize as varchar) converts the type of the variable to a varchar type
• Select CEILING(50.0/3) Rounding up, here the return value is 17, notice here the divisor or dividend must have a numeric type, otherwise it is not 17 but 16, hands-on try to know
• Select floor(50.0/3) or Select floor(3 rounding down, where the return value is 16, note that the divisor or divisor does not need to distinguish between the numeric type, I tested
• STR() returns character data converted from numeric data , meaning converting a number to a string

SQL Server knowledge Point record sharing