Boolean
Learn and explore the use of the boolean data type with the coding example.
We'll cover the following
The boolean data type was the topic of the “Three-Valued Logic” chapter earlier, with the SQL boolean truth table that includes the values true
, false
, and null
, and it’s important enough to warrant another inclusion here:
a │ b │ a=b │ op │ result
═══════╪═══════╪═══════╪═══════════════╪══════════
true │ true │ true │ true = true │ is true
true │ false │ false │ true = false │ is false
true │ ¤ │ ¤ │ true = null │ is null
false │ true │ false │ false = true │ is false
false │ false │ true │ false = false │ is true
false │ ¤ │ ¤ │ false = null │ is null
¤ │ true │ ¤ │ null = true │ is null
¤ │ false │ ¤ │ null = false │ is null
¤ │ ¤ │ ¤ │ null = null │ is null
(9 rows)
Aggregates
We can have tuple attributes as booleans too, and PostgreSQL includes specific aggregates for them:
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