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  2. Data definition language - Wikipedia

    en.wikipedia.org/wiki/Data_definition_language

    A commonly used CREATE command is the CREATE TABLE command. The typical usage is: CREATE TABLE [table name] ( [column definitions]) [table parameters] The column definitions are: A comma-separated list consisting of any of the following; Column definition: [column name] [data type] {NULL | NOT NULL} {column options}

  3. Check constraint - Wikipedia

    en.wikipedia.org/wiki/Check_constraint

    A NOT NULL constraint is functionally equivalent to the following check constraint with an IS NOT NULL predicate: . CHECK (column IS NOT NULL) Some relational database management systems are able to optimize performance when the NOT NULL constraint syntax is used as opposed to the CHECK constraint syntax given above.

  4. Help:Creating tables - Wikipedia

    en.wikipedia.org/wiki/Help:Creating_tables

    See Help:Sortable tables about rank columns and row numbers. See also: Commons:Convert tables and charts to wiki code or image files. See the section on updating List of countries by incarceration rate. Launch the visual editor. In the column you are copying click the header cell or whatever top cell you want.

  5. Nullable type - Wikipedia

    en.wikipedia.org/wiki/Nullable_type

    Nullable types are a feature of some programming languages which allow a value to be set to the special value NULL instead of the usual possible values of the data type.In statically typed languages, a nullable type is an option type, [citation needed] while in dynamically typed languages (where values have types, but variables do not), equivalent behavior is provided by having a single null ...

  6. Help:Introduction to tables with Wiki Markup/All - Wikipedia

    en.wikipedia.org/wiki/Help:Introduction_to...

    The easiest way to insert a new table is to use the editing toolbar that appears when you edit a page (see image above). Clicking the button will open a dialog where you define what you want in your new table. Once you've chosen the number of rows and columns, the wiki markup text for the table is inserted into the article.

  7. Database object - Wikipedia

    en.wikipedia.org/wiki/Database_object

    Tables, a set of values organized into rows and columns; Indexes, a data structure providing faster queries (at the expense of slower writing and storage to maintain the index structure) Views, a virtual table that is made as it is queried; Synonyms, alternate names for a table, view, sequence or other object in a database

  8. Help:Table/Advanced - Wikipedia

    en.wikipedia.org/wiki/Help:Table/Advanced

    This is because the table captions will not be correctly placed in mobile portrait view, or other narrow mobile screens, when the tables wrap. This is especially noticeable if the caption is longer. In that case when one table drops below the other, then the caption will be severely wrapped above only the first column of the table.

  9. 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 ...