Follow our table rules: columns and datatypes

You SHOULD:-

• Specify the nullability on columns.

• Define column data types (such as VARCHAR and CHAR) appropriately.

• Specify the length of a character column, even if you want it to be one. This rule applies when also declaring or casting variable datatypes.

• Use fixed-length datatypes rather than declaring variables as variable length of length 1 or 2.

• Include the precision and scale (when supported) when specifying numeric types. This prevents you being bound to the default values.

• Follow good database design practices. And if you consider yourself an 'Accidental DBA' be sure to read the 'Accidental DBA guide'!

You SHOULD NOT:-

• Use the CHAR or NCHAR data type for columns that permit NULL values.

• Use VARCHAR(MAX) when unnecessary.

• Use the TEXT or NTEXT datatypes.

• Declare variables without a datatype length. For example, DECLARE @MyVar VARCHAR; is to be avoided.

• Use inappropriate datatypes. For example, storing numbers or dates as VARCHAR.