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DELETE requires a shared table lock; Triggers fire; DELETE can be used in the case of: database link; DELETE returns the number of records deleted; Transaction log - DELETE needs to read records, check constraints, update block, update indexes, and generate redo / undo. All of this takes time, hence it takes time much longer than with TRUNCATE
all rows for which the predicate in the WHERE clause is True are affected (or returned) by the SQL DML statement or query. Rows for which the predicate evaluates to False or Unknown are unaffected by the DML statement or query. The following query returns only those rows from table mytable where the value in column mycol is greater than 100.
A filesystem ACL is a data structure (usually a table) containing entries that specify individual user or group rights to specific system objects such as programs, processes, or files. These entries are known as access-control entries (ACEs) in the Microsoft Windows NT, [4] OpenVMS, and Unix-like operating systems such as Linux, macOS, and ...
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 ...
rm deletes the file specified after options are added. Users can use a full path or a relative file path to specify the files to delete. rm doesn't delete a directory by default. [13] rm foo deletes the file "foo" in the directory the user is currently in. rm, like other commands, uses options to specify how it will behave:
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In order not to fill the data store with useless information, there is a policy to remove tombstones completely. For this, the system checks the age of the tombstone and removes it after a prescribed time has elapsed. In Apache Cassandra, this elapsed time is set with the GCGraceSeconds parameter [1] and the process is named Compaction. [2]
From clauses are very common, and will provide the rowset to be exposed through a Select statement, the source of values in an Update statement, and the target rows to be deleted in a Delete statement. [1] FROM is an SQL reserved word in the SQL standard. [2] The FROM clause is used in conjunction with SQL statements, and takes the following ...