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43 lines
1.0 KiB
Plaintext
43 lines
1.0 KiB
Plaintext
SQL Language Extension: COALESCE
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Function:
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Allow a column value to be calculated by a number of expressions,
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the first expression returning a non NULL value is returned as the
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column value
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Author:
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Arno Brinkman <firebird@abvisie.nl>
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Format:
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<case abbreviation> ::=
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| COALESCE <left paren> <value expression> { <comma> <value expression> }... <right paren>
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Syntax Rules:
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1) COALESCE (V1, V2) is equivalent to the following <case specification>:
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CASE WHEN V1 IS NOT NULL THEN V1 ELSE V2 END
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2) COALESCE (V1, V2,..., Vn), for n >= 3, is equivalent to the following
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<case specification>:
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CASE WHEN V1 IS NOT NULL THEN V1 ELSE COALESCE (V2,...,Vn) END
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Notes:
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See also README.data_type_results_of_aggregations.txt
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Examples:
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A)
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SELECT
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PROJ_NAME AS Projectname,
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COALESCE(e.FULL_NAME,'[> not assigned <]') AS Employeename
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FROM
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PROJECT p
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LEFT JOIN EMPLOYEE e ON (e.EMP_NO = p.TEAM_LEADER)
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B)
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SELECT
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COALESCE(Phone,MobilePhone,'Unknown') AS "Phonenumber"
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FROM
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Relations
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