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  2. SQL syntax - Wikipedia

    en.wikipedia.org/wiki/SQL_syntax

    Each column in an SQL table declares the type(s) that column may contain. ANSI SQL includes the following data types. [14] Character strings and national character strings. CHARACTER(n) (or CHAR(n)): fixed-width n-character string, padded with spaces as needed; CHARACTER VARYING(n) (or VARCHAR(n)): variable-width string with a maximum size of n ...

  3. Comparison of relational database management systems - Wikipedia

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

    8,060 bytes / 2 TB 6: 1,024 / 30,000(with sparse columns) 2 GB / Unlimited (using RBS/FILESTREAM object) 2 GB 6: 126 bits 2: 0001 9999 128 Microsoft SQL Server Compact (Embedded Database) 4 GB 4 GB 8,060 bytes 1024 2 GB 4000 154 bits 0001 9999 128 Mimer SQL: Unlimited Unlimited 16000 (+lob data) 252 Unlimited 15000 45 digits 0001-01-01 9999-12 ...

  4. Surrogate key - Wikipedia

    en.wikipedia.org/wiki/Surrogate_key

    A surrogate key is frequently a sequential number (e.g. a Sybase or SQL Server "identity column", a PostgreSQL or Informix serial, an Oracle or SQL Server SEQUENCE or a column defined with AUTO_INCREMENT in MySQL). Some databases provide UUID/GUID as a possible data type for surrogate keys (e.g. PostgreSQL UUID [3] or SQL Server ...

  5. xplorer² - Wikipedia

    en.wikipedia.org/wiki/Xplorer²

    Later versions support multi-folder browsing in side-by-side panels (aka Miller columns), detect duplicate and similar files and pictures to clean up hard disk space. xplorer² comes in two paid varieties, professional and ultimate.

  6. MinHash - Wikipedia

    en.wikipedia.org/wiki/MinHash

    This subset h (k) (S) is used as a signature for the set S, and the similarity of any two sets is estimated by comparing their signatures. Specifically, let A and B be any two sets. Then X = h ( k ) ( h ( k ) ( A ) ∪ h ( k ) ( B )) = h ( k ) ( A ∪ B ) is a set of k elements of A ∪ B , and if h is a random function then any subset of k ...

  7. Prepared statement - Wikipedia

    en.wikipedia.org/wiki/Prepared_statement

    The consequence of this is that a different query plan is compiled and stored for each different length. In general, the maximum number of "duplicate" plans is the product of the lengths of the variable length columns as specified in the database. For this reason, it is important to use the standard Add method for variable length columns: command.

  8. Data deduplication - Wikipedia

    en.wikipedia.org/wiki/Data_deduplication

    The reasons for this are two-fold: First, data deduplication requires overhead to discover and remove the duplicate data. In primary storage systems, this overhead may impact performance. The second reason why deduplication is applied to secondary data, is that secondary data tends to have more duplicate data.

  9. Merge (SQL) - Wikipedia

    en.wikipedia.org/wiki/Merge_(SQL)

    Additionally there is a single-row version, UPDATE OR INSERT INTO tablename (columns) VALUES (values) [MATCHING (columns)], but the latter does not give you the option to take different actions on insert versus update (e.g. setting a new sequence value only for new rows, not for existing ones.)