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15 Μαρ 2012 · select decode(type_id, null, 'Unknown', type_id), name, count(*) from. (. select 'asdf' type_id, 'name1' name from dual union all. select 'asdf' type_id, 'name2' name from dual union all. select null type_id, 'name3' name from dual. ) test_table. group by type_id,name;
1 Ιουν 2023 · Oracle DECODE Function with NULL Values. As I mentioned above, the Oracle DECODE function is an exception to other functions in how it handles NULL values. It treats a NULL expression and NULL search as equal (so NULL == NULL). So, this example will return 1: SELECT DECODE(NULL, NULL, 1, 0) FROM DUAL;
Oracle DECODE() function and NULL. NULL cannot be compared to anything even NULL. However, DECODE() function treats two null values are being equal. The following statement returns the string Equal: SELECT DECODE (NULL, NULL, 'Equal', 'Not equal') FROM dual; Code language: SQL (Structured Query Language) (sql)
This Oracle tutorial explains how to use the Oracle / PLSQL DECODE function with syntax and examples. The Oracle / PLSQL DECODE function has the functionality of an IF-THEN-ELSE statement.
Purpose. DECODE compares expr to each search value one by one. If expr is equal to a search, then Oracle Database returns the corresponding result. If no match is found, then Oracle returns default. If default is omitted, then Oracle returns null.
The DECODE function is not specifically for handling null values, but it can be used in a similar way to the NVL function, as shown by the following example. SQL> SELECT id, DECODE(col1, NULL, 'ZERO', col1) AS output FROM null_test_tab ORDER BY id; ID OUTPUT ----- ----- 1 ONE 2 ZERO 3 ZERO 4 ZERO 4 rows selected. SQL> NVL2
The DECODE function compares the expression with each searchN value sequentially. If a match is found, it returns the corresponding resultN value. If no match is found and a default value is provided, the function returns the default value; otherwise, it returns NULL.
