SQL conditional functions

The InfluxDB SQL implementation supports the following conditional functions for conditionally handling null values:

• coalesce
• nullif

coalesce

Returns the first of its arguments that is not null. Returns null if all arguments are null. This function is often used to substitute a default value for null values.

coalesce(expression1[, ..., expression_n])

Arguments

• expression1, expression_n: Expression to use if previous expressions are null. Can be a constant, column, or function, and any combination of arithmetic operators. Pass as many expression arguments as necessary.

SELECT
  val1,
  val2,
  val3,
  coalesce(val1, val2, val3, 'quz') AS coalesce
FROM
  (values ('foo', 'bar', 'baz'),
          (NULL, 'bar', 'baz'),
          (NULL, NULL, 'baz'),
          (NULL, NULL, NULL)
  ) data(val1, val2, val3)

nullif

Returns null if expression1 equals expression2; otherwise it returns expression1. This can be used to perform the inverse operation of coalesce.

nullif(expression1, expression2)

Arguments

• expression1: Expression to compare and return if equal to expression2. Can be a constant, column, or function, and any combination of arithmetic operators.
• expression2: Expression to compare to expression1. Can be a constant, column, or function, and any combination of arithmetic operators.

SELECT
  value,
  nullif(value, 'baz') AS nullif
FROM
  (values ('foo'),
          ('bar'),
          ('baz')
  ) data(value)