Editing SQL (section)

===Null===
The concept of [[Null (SQL)|Null]] is the subject of some [[Null (SQL)#Criticisms|debate]]. The Null marker indicates the absence of a value, and is distinct from a value of 0 for an integer column or an empty string for a text column. The concept of Nulls enforces the [[Null (SQL)#Comparisons with NULL and the three-valued logic (3VL)|3-valued-logic in SQL]], which is a concrete implementation of the general [[Three-valued logic|3-valued logic]].<ref name="Early History" />