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This list includes SQL reserved words – aka SQL reserved keywords, [1] [2] as the SQL:2023 specifies and some RDBMSs have added. Reserved words in SQL and related products In SQL:2023 [ 3 ]
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 ...
Formats that use delimiter-separated values (also DSV) [2]: 113 store two-dimensional arrays of data by separating the values in each row with specific delimiter characters. Most database and spreadsheet programs are able to read or save data in a delimited format.
SELECT list is the list of columns or SQL expressions to be returned by the query. This is approximately the relational algebra projection operation. AS optionally provides an alias for each column or expression in the SELECT list. This is the relational algebra rename operation. FROM specifies from which table to get the data. [3]
This is useful for many things. For example; for quickly updating country lists, or adding/updating a rank column, or copying a list of full names for states or countries. See Help:Sortable tables about rank columns and row numbers. See also: Commons:Convert tables and charts to wiki code or image files.
The Null marker indicates the absence of a value, and is distinct from a value of 0 for an integer column or an empty string for a text column. The concept of Nulls enforces the 3-valued-logic in SQL, which is a concrete implementation of the general 3-valued logic. [12]
In a relational database, a column is a set of data values of a particular type, one value for each row of a table. [1] A column may contain text values, numbers, or even pointers to files in the operating system. [2] Columns typically contain simple types, though some relational database systems allow columns to contain more complex data types ...
Does not free the space occupied by the data in the table (in the TABLESPACE) Does not reset the SEQUENCE value assigned to the table; DELETE works much slower than TRUNCATE; You can undo the operation of removing records by using the ROLLBACK command; DELETE requires a shared table lock; Triggers fire; DELETE can be used in the case of ...