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The SELECT statement has many optional clauses: SELECT list is the list of columns or SQL expressions to be returned by the query. This is approximately the relational algebra projection operation. AS optionally provides an alias for each column or expression in the SELECT list. This is the relational algebra rename operation.
The rename command is supported by Tim Paterson's SCP 86-DOS. [26] On MS-DOS, the command is available in versions 1 and later. [27] DR DOS 6.0 also includes an implementation of the ren and rename commands. [28] In Windows PowerShell, ren is a predefined command alias for the Rename-Item Cmdlet which basically serves the same purpose. [29]
Oracle Corporation calls these variables "substitution variables". Programmers can use them anywhere in a SQL or PL/SQL statement or in SQL Plus commands. They can be populated by a literal using DEFINE or from the database using the column command. predefined variables, prefixed with an underscore ('_') [10]
The relational algebra uses set union, set difference, and Cartesian product from set theory, and adds additional constraints to these operators to create new ones.. For set union and set difference, the two relations involved must be union-compatible—that is, the two relations must have the same set of attributes.
An alias is a feature of SQL that is supported by most, if not all, relational database management systems (RDBMSs).Aliases provide users with the ability to reduce the amount of code required for a query, and to make queries simpler to understand.
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In computing, rename refers to the altering of a name of a file. This can be done manually by using a shell command such as ren or mv , or by using batch renaming software that can automate the renaming process.
Rename may refer to: Rename (computing), rename of a file on a computer; RENAME (command), command to rename a file in various operating systems; Rename (relational algebra), unary operation in relational algebra; Company renaming, rename of a product; Name change, rename of a person; Geographical renaming, rename of a geographical location