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{{Short description|Marker used in SQL databases to indicate a value does not exist}}
[[File:Db null.png|300px|thumb|right|The Greek lowercase [[Omega|omega (ω)]] character is used to represent Null in [[database theory]].]]
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In [[SQL]], '''null''' or '''NULL''' is a special marker used to indicate that a data value does not exist in the [[database]]. Introduced by the creator of the [[Relational model|relational]] database model, [[E. F. Codd]], SQL null serves to fulfil the requirement that all ''true relational database management systems ([[Relational database#RDBMS|RDBMS]])'' support a representation of "missing information and inapplicable information". Codd also introduced the use of the lowercase Greek [[omega]] (ω) symbol to represent null in [[database theory]]. In SQL, <code>NULL</code> is a [[List of SQL reserved words|reserved word]] used to identify this marker.
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