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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;
15 Μαρ 2012 · 3 Answers. Sorted by: 17. 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;
9 Ιαν 2014 · SELECT 1 FROM DUAL WHERE NVL (NULL, '-1') = NVL (NULL, '-1') SELECT 1 FROM DUAL WHERE DECODE (NULL, NULL, '1', '0') = '1'. Both will evaluate nulls as being equal. I was just curious which would perform better as I have to have about 30 of these statements together in a case statement.
The DECODE function returns a value that is the same datatype as the first result in the list. If the first result is NULL, then the return value is converted to VARCHAR2. If the first result has a datatype of CHAR, then the return value is converted to VARCHAR2.
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
9 Απρ 2012 · With 19c, I didn't check it on another version, DECODE is converted in a join operation depending on the column definition. CREATE TABLE t1 (c_not_n NUMBER NOT NULL, c_null NUMBER); SELECT * FROM t1 a, t1 b WHERE decode(a.c_null,b.c_null,1)=1; => access(SYS_OP_MAP_NONNULL(A.C_NULL)=SYS_OP_MAP_NONNULL(B.C_NULL)) SELECT * FROM t1 a, t1 b
SELECT DECODE (NULL, NULL, 'Equal', 'Not equal') FROM dual; Code language: SQL (Structured Query Language) (sql) In this tutorial, you have learned how to use the Oracle DECODE() function to add procedure if-then-else logic to SQL queries.
