columns in database table contain data with same

Database Learning (4) -- create and update a data table 1 Database Learning (3) -- create and delete a database http://www.bkjia.com/database/201305/207489.html data table is a level object for operations in a relational database. In relational

Introduction: There is a computed in Microsoft SQL Server Columns columns. The value of this column is computed by an expression that refers to the value of the other columns of the same table. For example, there is a servicelog table containing

Http://www.cnblogs.com/gaizai/archive/2010/01/11/1644358.html   Before I start, I want to talk about several concepts. Overwrite Query] When an index contains all the columns referenced by a query, it is usually called "Overwrite query ". [Index

Introduction: When you add a TableAdapter to a typed dataset (Typed DataSet), the schema of the corresponding DataTable is already defined by the TableAdapter main query. For example, if the main query returns a, b,c these 3 domains, then The

The original: "Bi thing-the art of data" understanding Dimension Data Warehouse-fact table, dimension table, aggregation tableFact tableIn a multidimensional data warehouse, a table that holds a detailed value or fact for a measure is called a fact

Fact tableIn a multidimensional data warehouse, a table that holds a detailed value or fact for a measure is called a fact table. A fact table that stores sales and sales by state, product, and month has 5 columns that are conceptually similar to

Directly with Update aaaaa AA set aa.f = (AA.A+AA.B) on the line=======================================The new knowledge--Virtual columnsThe advantage of a virtual column is that if c=a+b inserts the data, the value is only inserted into the a=1,b=2;

We know that if we use MySQL, when the amount of database data reaches a certain amount of data, we will consider the database to do the sub-table, and other operations, but under what circumstances to do how to slice, the following table

For example, a table in a database has three columns, and one column cannot be empty. The other two columns are allowed to be empty, after I find all the data in this table, fill it into a datatable, now I am viewing the columns of this datatable

1. Access Method: This step includes storing and retrieving records from files.2. Alias (alias): Another name of an attribute. In SQL, you can replace the table name with an alias.3. Alternate keys (backup key, ER/link model): no candidate key is