SQL - Boolean

Data System Architecture


The Boolean data type in SQL is a Three-valued logic (3VL) boolean with:

  • true
  • false
  • and unknown (Stored with a SQL Null)

In SQL, the unkown is the output of a comparisons with the NULL value where null is not equal to null


The string key words TRUE and FALSE are the SQL-compliant string representation.

Documentation / Reference

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Data System Architecture
SQL - Null

NULL value in SQL represents missing data in SQL. NULL has its own data domain and implements therefore its own behavior. The most important one being that: An equality comparison of two NULL values...
Data System Architecture
Three-valued logic (3VL)

A three-valued logic implements a boolean as having three possible values: true, false and some indeterminate third value. This third value comes in play when you want to retrieve a Boolean...

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