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  2. Comparison of relational database management systems - Wikipedia

    en.wikipedia.org/wiki/Comparison_of_relational...

    Max DB size Max table size Max row size Max columns per row Max Blob/Clob size Max CHAR size Max NUMBER size Min DATE value Max DATE value Max column name size Informix Dynamic Server: ≈0.5 YB 12: ≈0,5YB 12: 32,765 bytes (exclusive of large objects) 32,765 4 TB 32,765 14: 10 125 13: 01/01/0001 10: 12/31/9999 128 bytes Ingres: Unlimited ...

  3. Cardinality (SQL statements) - Wikipedia

    en.wikipedia.org/wiki/Cardinality_(SQL_statements)

    In SQL (Structured Query Language), the term cardinality refers to the uniqueness of data values contained in a particular column (attribute) of a database table. The lower the cardinality, the more duplicated elements in a column. Thus, a column with the lowest possible cardinality would have the same value for every row.

  4. Relational database - Wikipedia

    en.wikipedia.org/wiki/Relational_database

    In SQL, an INNER JOIN prevents a cartesian product from occurring when there are two tables in a query. For each table added to a SQL Query, one additional INNER JOIN is added to prevent a cartesian product. Thus, for N tables in an SQL query, there must be N−1 INNER JOINS to prevent a cartesian product.

  5. SQL - Wikipedia

    en.wikipedia.org/wiki/SQL

    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 ...

  6. Wikipedia:Request a query/Tips and schemas - Wikipedia

    en.wikipedia.org/wiki/Wikipedia:Request_a_query/...

    Actor table - Be aware that there is a table called actor, with fields actor_id and actor_name (username). Instead of JOINing the user table, you will often need to JOIN the actor table instead. To get a user_name, instead of joining both the actor and user tables, you can join just actor and then select actor_name.

  7. Check constraint - Wikipedia

    en.wikipedia.org/wiki/Check_constraint

    A check constraint is a type of integrity constraint in SQL which specifies a requirement that must be met by each row in a database table. The constraint must be a predicate . It can refer to a single column, or multiple columns of the table.

  8. Bigtable - Wikipedia

    en.wikipedia.org/wiki/Bigtable

    When Table size threaten to grow beyond a specified limit, the tablets may be compressed using the algorithm BMDiff [13] [14] and the Zippy compression algorithm [15] publicly known and open-sourced as Snappy, [16] which is a less space-optimal variation of LZ77 but more efficient in terms of computing time. The locations in the GFS of tablets ...

  9. HeidiSQL - Wikipedia

    en.wikipedia.org/wiki/HeidiSQL

    Currently running processes to analyze executed SQL and to kill bad processes; View command-statistics with percentage indicator bars per SQL command; Databases. View all databases on the server, connect to a single database to work with its tables and data; View connected databases' total and table size in KB/MB/GB within the database/table ...