oracle sql not null

VARCHAR2 (20): = 'a ';BEGINIF n1 Dbms_output.put_line ('ELSEDbms_output.put_line ('= ');End if;END; Output: = 6) work, especially in report development. In SQL statements involving quantity and amount statistics, the NVL function is used to ignore NULL values. 4. Usage of related NULL functions:1) NVL (p1, p2) function. If p1 is

; -Result: 0 rows How can this happen? All becausenullIs an "unknown" type. That is to say, using the regular comparison operator (normal conditional operators)nullIt is meaningless to compare with other values.NullOr equalNull(Approximate understanding: an unknown value cannot be equal to an unknown value. The relationship between the two is also unknown. Otherwise, it will be messy in mathematics and logic ). -Note:: The following SQL is s

two is also unknown, 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; 12345678910 select null > 0;– result: nullselect null – result: nullselect null = 0;– resu

Null indicates an ambiguous or unknown column value. Test Table: testnull (ID varchar (32 )) Database: Sybase asa11.0 Row data (''), (null) When the database option ansinull is true (which is also the default option of the ASA database, Select * From testnull where id = NULL Select * From testnull where ID! = NULL Th

Label:When we don't know what the data is, it is unknown, it can be null, we call it null, and in Oracle, the table column with null values is zero in length.Oracle allows fields of any one data type to be empty, except for the following two scenarios:1, primary key field (primary key),2. A field with a NOT

'); 3 END; 4/ Pl/sql procedure successfully completed. Sql> VAR v_num Number Sql> BEGIN 2 dbms_redefinition. Copy_table_dependents (USER, ' T ', ' t_inter ', 3 dbms_redefinition. Cons_orig_params, True, True, True, FALSE,: V_num, True); 4 End; 5/ BEGIN * ERROR at line 1: Ora-01442:column to being modified to not

this? Everything just because null is a type that represents an "unknown". In other words, it is meaningless to compare null with other values using the regular comparison operator (normal conditional operators). Null is also not equal to NULL (approximate understanding: The unknown value cannot equal the unknown valu

Oracle's use of null in not in In the past, I also summarized some Oracle NULL problems. It happened that I saw another point that I didn't find before when I was reading the book, that is the question of using null in not in. SQL> select * from dept; DEPTNO DNAME LOC-------

Oracle determines whether the varchar2 type is null.VV_LIST: = 'dsssfdfdsfds ';IF (VV_LIST DBMS_OUTPUT.PUT_LINE ('ppppppppppppppp ');ELSEDBMS_OUTPUT.PUT_LINE ('bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb ');End if; The result is printed with bbbbbbbbbbbbbbbbbbbbbbbbbb. IF (''is null) THENDbms_output.put_line (''' is null ');End if;Output: ''is nullThis indicates that ''is

column collection PRIMARY KEY has an automatically defined UNIQUE constraint Note that each table can have multiple UNIQUE constraints, but only one PRIMARY KEY constraint per table The following SQL creates a unique constraint in the "id_p" column when the "Persons" table is created: Mysql CREATE TABLE Persons ( id_p int not NULL, LastName varchar (255) is not

To fix the reason for the security audit, found that there is a xs$null user in the database, try to modify the password for it, found an error. Even the SYS user cannot modify the password of the Xs$null User: Sql>--11.2.0.4sql> alter user xs$null identified by Oracle;Alte

; , NB Sp CHAR (2) sql> ALTER TABLE person modify pname not null; The table has changed. sql> desc person;is the name empty?Type----------------------------------------- -------- ------------------PID not NULL number (4)PNAME not NULL VARCHAR2 (20)Psex CH

Replace NULL in SQLServer, Oracle, and MySQL. This article describes how to replace NULL in SQL Server, Oracle, and MySQL. In SQL Server Oracle MySQL what should I do if I find a

It is slow to add a NOT null field before 11g. It was soon after 11g. Let's do a test first and then explore the principles.Sql> select * from V$version;BANNER----------------------------------------------------------------Oracle Database 10g Enterprise Edition Release 10.2.0.1.0-64biPL/SQL Release 10.2.0.1.0-productionCORE 10.2.0.1.0 ProductionTNS for 64-bit win

When the default value getdate () is set, the new data is still null. This problem does not occur when you use the SQL statement insert, but the problem occurs when you use the LINQ to SQL statement. Solution: http://msdn.microsoft.com/zh-cn/library/system.data.linq.mapping.columnattribute.isdbgenerated.aspx [Column (storage = " _ Orderid " , Autosync = auto

This is a frequently asked question. Especially if the customer used Oracle before, when using SQL Server, there will be The question is that SQL Server and Oracle behave differently in processing null values. In Oracle, the

Tags: single quote sum requires error ROM tab foreign language nvarchar(ii) SQL statement fuzzy query NULL processing aggregate function My own study notes, reproduced please indicate the source, thank you!---sauerkraut SQL: Structured Query Language (structured Query Language), a standard language for relational database management systems. Sybase and Mircosoft

operator such as =, DECLAREN1 VARCHAR2 (20);N2 VARCHAR2 (): = ' a ';BEGINIF N1 Dbms_output.put_line (' ELSEDbms_output.put_line (' = ');END IF;END; Output: = 6) in the work. Especially in report development. In SQL statements involving quantity, amount statistics, and so on, the NVL function is used to ignore null values. 4, the related NULL function uses the