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In relational databases, the log trigger or history trigger is a mechanism for automatic recording of information about changes inserting or/and updating or/and deleting rows in a database table. It is a particular technique for change data capturing , and in data warehousing for dealing with slowly changing dimensions .
Many FOSS software tools allow modelling of DB layout/schemes like this. Visual representation often may also be exported as a production-ready source code made in DB-compatible languages like SQL . The database schema is the structure of a database described in a formal language supported typically by a relational database management system ...
We create log records of the form (Sequence Number, Transaction ID, Page ID, Redo, Undo, Previous Sequence Number). The Redo and Undo fields keep information about the changes this log record saves and how to undo them. The Previous Sequence Number is a reference to the previous log record that was created for this transaction.
Creating complex queries using query-by-example (QBE) Searching globally in a database or a subset of it; Transforming stored data into any format using a set of predefined functions, like displaying BLOB-data as image or download-link; Live charts to monitor MySQL server activity like connections, processes, CPU/memory usage, etc.
The changes are first recorded in the log, which must be written to stable storage, before the changes are written to the database. [2] The main functionality of a write-ahead log can be summarized as: [3] Allow the page cache to buffer updates to disk-resident pages while ensuring durability semantics in the larger context of a database system.
The name is commonly used when creating a query to the database. The Database Source Name (DSN) does not have to be the same as the filename for the database. For example, a database file named "friends.mdb" could be set up with a DSN of "school". Then DSN "school" would then be used to refer to the database when performing a query.
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The terms data dictionary and data repository indicate a more general software utility than a catalogue. A catalogue is closely coupled with the DBMS software. It provides the information stored in it to the user and the DBA, but it is mainly accessed by the various software modules of the DBMS itself, such as DDL and DML compilers, the query optimiser, the transaction processor, report ...