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In SQL, you can alias tables and columns. A table alias is called a correlation name, according to the SQL standard. [1] A programmer can use an alias to temporarily assign another name to a table or column for the duration of the current SELECT query. Assigning an alias does not actually rename the column or table.
With the same table, the query SELECT C1 FROM T will result in the elements from the column C1 of all the rows of the table being shown. This is similar to a projection in relational algebra , except that in the general case, the result may contain duplicate rows.
When it is completely normalized along all the dimension tables, the resultant structure resembles a snowflake with the fact table in the middle. The principle behind snowflaking is normalization of the dimension tables by removing low cardinality attributes and forming separate tables. [1] The snowflake schema is similar to the star schema.
SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd [12] in the early 1970s. [13] This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasirelational database management system, System R, which a group at IBM San ...
A query includes a list of columns to include in the final result, normally immediately following the SELECT keyword. An asterisk ("*") can be used to specify that the query should return all columns of the queried tables. SELECT is the most complex statement in SQL, with optional keywords and clauses that include:
Fact_Sales is the fact table and there are three dimension tables Dim_Date, Dim_Store and Dim_Product. Each dimension table has a primary key on its Id column, relating to one of the columns (viewed as rows in the example schema) of the Fact_Sales table's three-column (compound) primary key (Date_Id, Store_Id, Product_Id).
This is a standalone product for developers to create data models for MySQL, SQL Server, Oracle, PostgreSQL and SQLite databases. Navicat Data Modeler allows users to visually design database structures, perform reverse/forward engineer process, import table structures from ODBC data sources, generate SQL files and print models to files, etc.
The C standard library provides a function called rename which does this action. [1] In POSIX, which is extended from the C standard, the rename function will fail if the old and new names are on different mounted file systems. [2] In SQL, renames are performed by using the CHANGE specification in ALTER TABLE statements.