SQL References

The following SQL statement shows how to copy the data from one column to another.

It will replace any existing values in the destination column, so be sure to know exactly what you’re doing and use the WHERE statement to minimize updates (e.g., WHERE destination_column IS NULL ).

UPDATE table 
SET destination_column = source_column
WHERE destination_column IS NULL

Returns the number of characters of the specified string expression, excluding trailing spaces.

To return the number of bytes used to represent an expression, use the DATALENGTH function.

The following example selects the number of characters and the data in FirstName column

SELECT LEN(FirstName) AS Length, FirstName
FROM Sales.vIndividualCustomer  
WHERE CountryRegionName = 'Australia';

Source: LEN (Transact-SQL) - SQL Server | Microsoft Docs

This function returns the number of bytes used to represent any expression.

To return the number of characters in a string expression, use the LEN function.

This example finds the length of the Name column in the Product table:

SELECT length = DATALENGTH(EnglishProductName), EnglishProductName  
FROM dbo.DimProduct  
ORDER BY EnglishProductName;  

Source: DATALENGTH (Transact-SQL) - SQL Server | Microsoft Docs

The SQL UPDATE Statement

The UPDATE statement is used to modify the existing records in a table.

UPDATE Syntax

UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;

SQL SET Keyword

The SET command is used with UPDATE to specify which columns and values should be updated in a table.

The following SQL updates the first category (CategoryID = 1) with a new Name and a new Type:

Example

UPDATE Category
SET Name = 'Article', Type = 'Premium'
WHERE CategoryID = 1;