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dev:sql:functions:case [2009/12/18 16:25] tdo |
dev:sql:functions:case [2010/07/27 20:05] els |
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| + | {{page>:top_add&nofooter&noeditbtn}} | ||
| + | {{page>:sql_bar&nofooter&noeditbtn}} | ||
| + | ====== Omnidex SQL Function: CASE ====== | ||
| + | ===== Description ===== | ||
| + | The CASE function performs simple IF ... THEN ... ELSE ... END logic within a function. Typically this is used to set a value based on a set of different conditions. The conditions are evaluated in the order they appear in the function until a condition proves TRUE, at which point the THEN expression is executed. If none of the conditions prove TRUE, then the final ELSE expression is executed. | ||
| + | |||
| + | This functions returns the same datatype as the THEN clauses in the function. All of the THEN expressions in a CASE statement must be of the same datatype. | ||
| + | |||
| + | ===== Syntax ===== | ||
| + | |||
| + | The CASE function supports two standard syntaxes: | ||
| + | |||
| + | CASE | ||
| + | WHEN conditional_expression_1 THEN scalar_expression_1 | ||
| + | WHEN conditional_expression_2 THEN scalar_expression_2 | ||
| + | ELSE scalar_expression | ||
| + | END | ||
| + | |||
| + | and | ||
| + | |||
| + | CASE scalar_expression_1 | ||
| + | WHEN scalar_expression_2 THEN scalar_expression_3 | ||
| + | WHEN scalar_expression_4 THEN scalar_expression_5 | ||
| + | ELSE scalar_expression_6 | ||
| + | END | ||
| + | |||
| + | |||
| + | == conditional_expression == | ||
| + | |||
| + | Required. A conditional expression using SQL language that must prove TRUE in order for the function to return the corresponding scalar expression. A conditional expression is generally equivalent to criteria used in a WHERE clause of a SQL SELECT statement, such as "state in ('CA','OR','WA')" or "birthdate >= 'Jan 1, 1980'. | ||
| + | |||
| + | == scalar_expression == | ||
| + | |||
| + | Required. An expression using SQL language that produces a value. A scalar expression is generally equivalent to a select item in the SQL SELECT statement, and can be a character expression, numeric expression or date expression. | ||
| + | |||
| + | ===== Example ===== | ||
| + | ==== Example 1: CASE against column values ==== | ||
| + | |||
| + | <code> | ||
| + | > select name, | ||
| + | >> gender, | ||
| + | >> case gender | ||
| + | >> when 'M' then 'Male' | ||
| + | >> when 'F' then 'Female' | ||
| + | >> else 'Did not specify' | ||
| + | >> end gender_desc | ||
| + | >> from individuals; | ||
| + | |||
| + | NAME G GENDER_DESC | ||
| + | -------------------------------------------------- - --------------- | ||
| + | MS. MARY LEWIS F Female | ||
| + | MRS. ALICE R TOLLIVER F Female | ||
| + | MR. SIDNEY K TOLLIVER M Male | ||
| + | MRS. JENNIFER J HOPKINS F Female | ||
| + | MR. CHARLIE HOPKINS M Male | ||
| + | MS. KIMBERLY BLUE F Female | ||
| + | KATHLEEN TUCKER F Female | ||
| + | </code> | ||
| + | ==== Example 2: CASE using complex expressions ==== | ||
| + | |||
| + | <code> | ||
| + | > select name, | ||
| + | >> gender, | ||
| + | >> birthdate, | ||
| + | >> case | ||
| + | >> when gender = 'M' and $compare_dates(birthdate, current_date, 'YY') < 18 | ||
| + | >> then 'Mstr.' | ||
| + | >> when gender = 'M' and $compare_dates(birthdate, current_date, 'YY') >= 18 | ||
| + | >> then 'Mr.' | ||
| + | >> when gender = 'F' and $compare_dates(birthdate, current_date, 'YY') < 18 | ||
| + | >> then 'Miss' | ||
| + | >> when gender = 'F' and $compare_dates(birthdate, current_date, 'YY') >= 18 | ||
| + | >> then 'Ms.' | ||
| + | >> else | ||
| + | >> '' | ||
| + | >> end salutation | ||
| + | >> from individuals; | ||
| + | |||
| + | NAME G BIRTHDATE SALUT | ||
| + | -------------------------------------------------- - ------------ ----- | ||
| + | MS. MARY LEWIS F 1938-07-14 Ms. | ||
| + | MRS. ALICE R TOLLIVER F 1957-11-22 Ms. | ||
| + | MR. SIDNEY K TOLLIVER M 1960-07-28 Mr. | ||
| + | MRS. JENNIFER J HOPKINS F 1929-08-22 Ms. | ||
| + | MR. CHARLIE HOPKINS M 1933-07-09 Mr. | ||
| + | MS. KIMBERLY BLUE F 1944-08-01 Ms. | ||
| + | KATHLEEN TUCKER F 2004-09-14 Miss | ||
| + | </code> | ||
| + | |||
| + | ====== Additional Resources ====== | ||
| + | |||
| + | See also: | ||
| + | {{page>dev:sql:functions:see_also_logic&noheader&nofooter&noeditbtn}} | ||
| + | |||
| + | |||
| + | {{page>:bottom_add&nofooter&noeditbtn}} | ||
| + | |||
| + | ===== | ||
| + | |||
| + | |||
| + | |||
| + | |||
| {{page>:top_add&nofooter&noeditbtn}} | {{page>:top_add&nofooter&noeditbtn}} | ||
| <html><div align="center"><span style="color:red">DRAFT</span></div></html> | <html><div align="center"><span style="color:red">DRAFT</span></div></html> | ||
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| ===== Example ===== | ===== Example ===== | ||
| ==== Example 1 Condition Expression ==== | ==== Example 1 Condition Expression ==== | ||
| - | <code SQL> | + | <code> |
| + | SELECT ... | ||
| CASE | CASE | ||
| - | WHEN PRODUCTS.CATEGORY < 30 THEN 'Furniture' | + | WHEN PRODUCTS.CATEGORY =30 THEN 'Furniture' |
| - | WHEN PRODUCTS.CATEGORY < 70 THEN 'Machines' | + | WHEN PRODUCTS.CATEGORY = 70 THEN 'Machines' |
| - | WHEN PRODUCTS.CATEGORY < 90 THEN 'Paper Products' | + | WHEN PRODUCTS.CATEGORY = 90 THEN 'Paper Products' |
| ELSE 'Office Supplies' | ELSE 'Office Supplies' | ||
| - | END | + | END; |
| </code> | </code> | ||
| + | |||
| ==== Example 2 Scalar Expression ==== | ==== Example 2 Scalar Expression ==== | ||
| <code SQL> | <code SQL> | ||
| Line 56: | Line 160: | ||
| from customers | from customers | ||
| where state in ('ca','co','ny','nj','az','fl','nv') | where state in ('ca','co','ny','nj','az','fl','nv') | ||
| - | order by state | + | order by state; |
| </code> | </code> | ||
| + | |||
| ==== Example 4 Select Statement with Scalar Expression ==== | ==== Example 4 Select Statement with Scalar Expression ==== | ||
| <code SQL> | <code SQL> | ||