Updating values in sql
TOP ( ) Specifies one or more table hints that are allowed for a target table. @ When referencing the Unicode character data types nchar, nvarchar, and ntext, 'expression' should be prefixed with the capital letter ' N'.If ' N' is not specified, SQL Server converts the string to the code page that corresponds to the default collation of the database or column.Specifies the temporary named result set or view, also known as common table expression (CTE), defined within the scope of the UPDATE statement.
Because of this indeterminacy, referencing other tables only within sub-selects is safer, though often harder to read and slower than using a join.  Set the value of column C1 in table T to 1, only in those rows where the value of column C2 is "a".
I have a database with account numbers and card numbers.
This is the UPDATE [Sales_Lead].[dbo].[Sales_Import] SET [Account Number] = (SELECT Retrieve Account Number.
Account Number FROM Retrieve Account Number WHERE [Sales_Lead].[dbo].[Sales_Import]. Lead ID) I think there is no need for the inner join.
In some databases, such as Postgre SQL, when a FROM clause is present, what essentially happens is that the target table is joined to the tables mentioned in the fromlist, and each output row of the join represents an update operation for the target table.