8.3.3 LOG
Given a base and antilogarithm, returns its logarithm.
- Organization of this subsection
(1) Specification format
scalar-function-LOG ::= LOG(base,target-data) base ::= value-expression target-data ::= value-expression
(2) Explanation of specification format
- base:
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Specifies the base of the logarithm.
The following rules apply:
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Specify the base in the form of a value expression. For details about value expressions, see 7.20 Value expression.
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Specify numeric data for the base. For details about numeric data, see (1) Numeric data in 6.2.1 List of data types.
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You cannot specify a value less than or equal to 0 for the base.
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If you specify 1 for the base, a divide-by-zero error is generated.
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You cannot specify a dynamic parameter by itself for the base.
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- target-data:
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Specify the target data (antilogarithm).
The following rules apply:
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Specify the target data in the form of a value expression. For details about value expressions, see 7.20 Value expression.
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Specify numeric data for the target data. For details about numeric data, see (1) Numeric data in 6.2.1 List of data types.
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You cannot specify a value less than or equal to 0 for the target data.
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You cannot specify a dynamic parameter by itself for the target data.
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(3) Rules
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The data type of the execution result is the DOUBLE PRECISION type.
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The NOT NULL constraint does not apply to the value of the execution result (the null value is allowed).
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If either the base or target data has a null value, the execution result will be a null value.
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The execution result of LOG(base,target-data) is equivalent to LN(target-data)/LN(base).
(4) Examples
- Example 1:
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Determine the common logarithm of the value of column C1 in table T1.
SELECT LOG(10,"C1") FROM "T1"
- Example 2:
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Determine the logarithm of the value of column C2 in table T1, using the value of column C1 as the base.
SELECT LOG("C1","C2") FROM "T1"