The following tables display how the AND, OR, NOT, and IS logical operators of SQL work in three-valued logic.

AND | TRUE | FALSE | UNKNOWN |
---|---|---|---|

TRUE | TRUE | FALSE | UNKNOWN |

FALSE | FALSE | FALSE | FALSE |

UNKNOWN | UNKNOWN | FALSE | UNKNOWN |

OR | TRUE | FALSE | UNKNOWN |
---|---|---|---|

TRUE | TRUE | TRUE | TRUE |

FALSE | TRUE | FALSE | UNKNOWN |

UNKNOWN | TRUE | UNKNOWN | UNKNOWN |

TRUE | FALSE | UNKNOWN |
---|---|---|

FALSE | TRUE | UNKNOWN |

IS | TRUE | FALSE | UNKNOWN |
---|---|---|---|

TRUE | TRUE | FALSE | FALSE |

FALSE | FALSE | TRUE | FALSE |

UNKNOWN | FALSE | FALSE | TRUE |

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