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====== Omnidex SQL Function: CASE ====== | ====== Omnidex SQL Function: CASE ====== | ||
===== Description ===== | ===== Description ===== | ||
- | The CASE function handles simple IF - THEN - ELSE logic at a select-item level. The WHEN conditions are evaluated in order until a condition proves TRUE, at which point the THEN expression is executed. All of the THEN expressions in a CASE statement must be of the same data type: numeric, character, or date. | + | 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 ===== | ===== Syntax ===== | ||
+ | |||
+ | The CASE function supports two standard syntaxes: | ||
+ | |||
CASE | CASE | ||
- | WHEN condition_expression THEN scalar_expression | + | WHEN conditional_expression_1 THEN scalar_expression_1 |
+ | WHEN conditional_expression_2 THEN scalar_expression_2 | ||
ELSE scalar_expression | ELSE scalar_expression | ||
END | END | ||
- | or | + | and |
CASE scalar_expression_1 | CASE scalar_expression_1 | ||
WHEN scalar_expression_2 THEN scalar_expression_3 | WHEN scalar_expression_2 THEN scalar_expression_3 | ||
- | ELSE scalar_expression_4 | + | WHEN scalar_expression_4 THEN scalar_expression_5 |
+ | ELSE scalar_expression_6 | ||
END | END | ||
- | ===== Example ===== | ||
- | ==== Example 1 ==== | + | == conditional_expression == |
- | CASE | + | |
- | WHEN PRODUCTS.CATEGORY < 30 THEN 'Furniture' | + | |
- | WHEN PRODUCTS.CATEGORY < 70 THEN 'Machines' | + | |
- | WHEN PRODUCTS.CATEGORY < 90 THEN 'Paper Products' | + | |
- | ELSE 'Office Supplies' | + | |
- | END | + | |
- | ==== Example 2 ==== | + | 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'. |
- | CASE DATES.MO | + | |
- | WHEN 'Jan' THEN 1 | + | |
- | WHEN 'Feb' THEN 2 | + | |
- | WHEN 'Mar' THEN 3 | + | |
- | WHEN 'Apr' THEN 4 | + | |
- | ELSE 0 | + | |
- | END | + | |
- | ==== Example 3 ==== | + | == scalar_expression == |
- | <code SQL> | + | 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. |
- | select company, | + | |
- | case | + | ===== Example ===== |
- | when customers.state='CA' then 'CALIFORNIA' | + | ==== Example 1: CASE against column values ==== |
- | when customers.state='CO' then 'COLORADO' | + | |
- | when customers.state='NY' then 'NEW YORK' | + | <code> |
- | when customers.state='NJ' then 'NEW JERSEY' | + | > select name, |
- | else 'OTHER' | + | >> gender, |
- | end | + | >> case gender |
+ | >> when 'M' then 'Male' | ||
+ | >> when 'F' then 'Female' | ||
+ | >> else 'Did not specify' | ||
+ | >> end gender_desc | ||
+ | >> from individuals; | ||
- | from customers | + | NAME G GENDER_DESC |
- | where state in ('ca','co','ny','nj','az','fl','nv') | + | -------------------------------------------------- - --------------- |
- | order by state | + | 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> | </code> | ||
- | ==== Example 4 ==== | + | ==== Example 2: CASE using complex expressions ==== |
- | <code SQL> | + | |
- | select company, contact, | + | |
- | case customers.state | + | <code> |
- | when 'AZ' then 'ARIZONA' | + | > select name, |
- | when 'FL' then 'FLORIDA' | + | >> gender, |
- | when 'NV' then 'NEVADA' | + | >> birthdate, |
- | else 'OTHER' | + | >> case |
- | end | + | >> 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}} | ||
- | from customers | ||
- | where company='systems' | ||
- | order by state | ||
- | </code? | ||
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+ | |||
+ | ===== | ||
+ |