select null from table in oracle

CREATE TABLE as SELECT * FROM and insert to select from two table copy statement differences[SQL]View PlainCopy Create table targer_table as select * from source_table INSERT INTO target_table (column1,column2) select Column1,column2

1 Introduction to null valuesNULL is a unique data type in the database. If a column in a record is NULL, the value of this column is unknown and uncertain. Since it is unknown, there are several possibilities. Therefore, NULL is not a definite

In the database, a null value is used to indicate that the actual value is unknown or meaningless. In a table, if a column in a row has no value, it is called NULL ). A null value can be returned for any data type column as long as the non-NULL or

Oracle in the database, null values are used to indicate a situation where the actual value is unknown or meaningless. In a table, if a column in a row has no value, it is called a null value (NULL). Columns of any data type can have null values if

Sometimes, because of project development, some tables in the SQLServer2005 must be synchronized to the Oracle database, which can be read by other systems. Data synchronization between different database types can be implemented using linked

---DQL: Data query statementsThe---Select statement must contain at least two words, namely the Select and from words.---the SELECT clause to specify the field to query.---the table that the FROM clause uses to customize the data source. The--select

Oracle CBO RBO Detailed url:http://blog.163.com/love-love-l/blog/static/21078304201010175035270/ Http://blog.csdn.net/cnham/archive/2010/04/13/5482318.aspx First part What is Table analysis. Simply put, it is the information that collects tables

In Oracle, a keyword is NULL, indicating that a value is unknown and uncertain. Since it is unknown, there are several possibilities. Therefore, NULL is not a definite In Oracle, a keyword is NULL, indicating that a value is unknown and uncertain.

When the string is empty, it is judged by where null is used. Example: CREATE TABLE Test(Stuno Number (Ten) primary key,Stuname VARCHAR2 (50))INSERT into Test (Stuno) VALUES (10)INSERT into Test (stuno,stuname) VALUES (11, ') SELECT * FROM test

The introduction of 1null value NULL is a unique data type in the database. When a column in a record is NULL, the value of this column is unknown and uncertain. Since it is unknown, there are several possibilities. Therefore, NULL is not a definite