oracle sql not null

Tags: while in mil create BSP rom a not tab oraYesterday in the QQ group to discuss a SQL optimization problem, the statement roughly as follows:Select A,min (B) from table group by A;--a,b does not have a NOT NULL constraint, column A has no null value, and column B has a null value.-There is a composite index ix_test

NVL (BONUS, 0.0) from EMPLOYEE; --The following two statements are equivalent to the SELECT case when BONUS isn't NULL THEN BONUS ELSE 0.0 end from EMPLOYEE; SELECT NVL2 (BONUS, BONUS, 0.0) from EMPLOYEE; If you want to find a total salary (basic salary + bonus) is greater than 3000 yuan employees, we will naturally write the following statement: SELECT * from EMPLOYEE WHERE SALARY + BONUS >= 3000.0; Unfortunately, this statement is not alway

Label:Oracle considers NULL to be the largest.In ascending order, by default, the null value is sorted back.The descending sort, by default, is preceded by a null value.To change the null value method:(1) Convert NULL to a specific value using the NVL function or the Decode

INSERT into Table (testcol) VALUES (') The Testcol field, in fact, has been designed to be not null at design time, but we need to understand that NULL and whitespace are different in SQL Server, that is, the above statement inserts an empty, but is not NULL, Only when we do not have the field in the INSERT statement w

(NULL), that is, to visualize NULL into a table. This is against common sense. Oracle cannot do it! How can this problem be solved? The version_list field is NULL because it is not initialized at all. So, can the problem be solved shortly after initialization of insert? Method 1: Use the following statement to insert

indexed, indexes will be used for operations. Instead of a full table scan. When a table is large, the efficiency is certainly higher than in and not in. This is why exists is recommended for SQL writing.Now let's take a look at the previous use of not in to find the results, but with not exits, We can find:SQL> select empno, ename from emp A where not exists (SELECT * FROM emp1 Bwhere B. job = A. job );EMPNO ENAME--------------------8888 DaveDave's

and deleting tables -- after creating a table, you can only add and delete tables, but cannot modify them. 2.1 Add alter table emp1 add constaint emp1_sal_ck check(salary > 0) 2.1.1 for not null, you do not need to add. You need to use modify: alter table emp1 modify (salary not null) 2.2 Delete alter table emp1 drop constaint emp1_sal_ck 2.3 invalidate a constraint: the constraint

Oracle uses orderby to sort null values When order by is used in Oracle for query and sorting, if there is a null value in the sorting field, the sorting result may not reach the expected result. For example: Select * from test order by age desc; Sort by age field in descending order. The result is as follows: Ch

The indp parameter is an indicator buffer and an array. Each element is a value of the sb2 type. This parameter is generally used for input. If this dynamic parameter is output, it is also used for output. In The indp parameter is an indicator buffer and an array. Each element is a value of the sb2 type. This parameter is generally used for input. If this dynamic parameter is output, it is also used for output. In Processing null in oci must be c

Processing null in oci must be completed through Indicator. Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 # Include # Include # Include # Include "include \ oci. h"# Include "include \ ociextp. h" # Define ERRGOTO (Recode) do \{\If (Recode! = 0 )\{\Goto ERR ;\}\} While (0) Void main (){ Int a = 0;OCIDefine * defhp1 = 0;OCIDefine * defhp2 = 0;Int blength = 40;Char B [40];Sb2 indicator; Text * s

How to import additional fields in Oracle as null values Q: We have migrated our Oracle database to a new environment. Some customer tables exist in two databases at the same time, but those tables in the new environment have some additional fields. Can you help me use the import/export tool? In this way, I can either import a new

, otherwise the math and logic will be messed up). – Note : The following SQL is suitable for MySQL, if it is Oracle, you need to add ... from dual; Select Null > 0; –result:null Select Null The correct way to compare a value to NULL is to use the IS keyword, and the is n

* *********** NUL, NVL2, and NULLIF usage in Oracle *************** NULL indicates null Value, or the value is invalid. 1. NVL (expr1, expr2) function expr /*********** NUL, NVL2, and NULLIF usage in Oracle ***************/NULL indicates is

('integer varray ['| I |'] '|' is null ');End if; End loop; End;/ The running result is as follows:/* The running is normal, and the display element is null, which is a conflict of Definitions */ Integer varray initialized [5]Integer varray [1] []Integer varray [1] is nullInteger varray [2] []Integer varray [2] is nullInteger varray [3] []Integer varray [3] is nullInteger varray [4] []Integer varray [4] i

In the Access Project (that is, the. ADP file) linked to an SQL Server database, the access function that you frequently use is usually not supported. But most of the time, you can use a Transact-SQL (T-SQL) function supported by SQL Server. One exception is that access's null