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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.
UPDATE table_name SET ... WHERE CURRENT OF cursor_name DELETE FROM table_name WHERE CURRENT OF cursor_name. The cursor must operate on an updatable result set in order to successfully execute a positioned update or delete statement. Otherwise, the DBMS would not know how to apply the data changes to the underlying tables referred to in the cursor.
In standard SQL:1999 hierarchical queries are implemented by way of recursive common table expressions (CTEs). Unlike Oracle's earlier connect-by clause, recursive CTEs were designed with fixpoint semantics from the beginning. [1] Recursive CTEs from the standard were relatively close to the existing implementation in IBM DB2 version 2. [1]
A new client process reusing this persistent connection will get the connection "as is". Any cleanup would need to be done by the new client process before it could make good use of the persistent connection, increasing the burden on the programmer. The persistent connection of the MySQLi extension however provides built-in cleanup handling code.