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SQLAlchemy offers tools for database schema generation, querying, and object-relational mapping. Key features include: A comprehensive embedded domain-specific language for SQL in Python called "SQLAlchemy Core" that provides means to construct and execute SQL queries. A powerful ORM that allows the mapping of Python classes to database tables.
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.
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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.
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.
Most modern machines do renaming by RAM indexing a map table with the logical register number. E.g., P6 did this; future files do this, and have data storage in the same structure. However, earlier machines used content-addressable memory (CAM) in the renamer. E.g., the HPSM RAT, or Register Alias Table, essentially used a CAM on the logical ...
Pylons Project is an open-source organization that develops a set of web application technologies written in Python.Initially the project was a single web framework called Pylons, but after the merger with the repoze.bfg framework under the new name Pyramid, the Pylons Project now consists of multiple related web application technologies.
In relational algebra, a rename is a unary operation written as / where: . R is a relation; a and b are attribute names; b is an attribute of R; The result is identical to R except that the b attribute in all tuples is renamed to a. [1]