SQL type conversion functions and text and image functions

Format:
CONVERT (datatype[(length)].expression[,style])
Parameter expression the converted data type, which can only be the length of the system data.
The maximum value for length is 255, and the default length is 30.
When converting a ddatetime or smalldatetime data type to character data, the style parameter is used to describe the converted string format.

Text and image functions as shown in the table:

Function	Parameters	Function
Texttptr	(column_name)	Returns a pointer to the first page of the text or image column as a varbinary data type and returns null if the text or image column has not been initialized with an INSERT or UPDATE statement
Textvalid	(' Table_name.column_name ', text_ptr)	Check the validity of the text_ptr pointer to the Table_name.column_name and return 1 if the pointer is valid, otherwise return 0