Reprinted: 2015-01-17 15:32:33
Http://www.cnblogs.com/FeiyueHang/archive/2011/03/08/1977729.html
1.NVL (EXPR1,EXPR2)
If EXPR1 is null, the function displays the value of EXPR2;
2.NVL2 (EXPR1,EXPR2,EXPR3)
If the value of EXPR1 is null, the function displays the value of EXPR3, NOT NULL, showing the value of EXPR2;
3.NULLIF (EXPR1,EXPR2)
Returns null if EXPR1=EXPR2, or returns the value of the first expression if unequal;
4.COALSECE (EXPR1,EXPR2,EXPR3)
If all is null, the function value is null, and if one is not NULL, the EXPRN is displayed; If none of the three items is empty, the first one is displayed;
5.
1 Case2 SELECTCust_last_name,3 CaseCredit_limit when - Then ' Low'4 when the Then ' High'5 ELSE 'Medium' END6 fromCustomers
Case similar to C language
6.DECODE
SELECTproduct_id, DECODE (warehouse_id,1, 'Southlake', 2, 'San Francisco', 3, 'New Jersey', 4, 'Seattle', 'non-domestic') "Location ofInventory " fromInventoriesWHEREproduct_id< 1775;
Oracle's functions for handling null values