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SELECT * FROM (SELECT ROW_NUMBER OVER (ORDER BY sort_key ASC) AS row_number, columns FROM tablename) AS foo WHERE row_number <= 10 ROW_NUMBER can be non-deterministic : if sort_key is not unique, each time you run the query it is possible to get different row numbers assigned to any rows where sort_key is the same.
A view is a relational table, and the relational model defines a table as a set of rows. Since sets are not ordered — by definition — neither are the rows of a view. Therefore, an ORDER BY clause in the view definition is meaningless; the SQL standard ( SQL:2003 ) does not allow an ORDER BY clause in the subquery of a CREATE VIEW command ...
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.
In relational databases a virtual column is a table column whose value(s) is automatically computed using other columns values, or another deterministic expression. Virtual columns are defined of SQL:2003 as Generated Column, [1] and are only implemented by some DBMSs, like MariaDB, SQL Server, Oracle, PostgreSQL, SQLite and Firebird (database server) (COMPUTED BY syntax).
An ORDER BY clause in SQL specifies that a SQL SELECT statement returns a result set with the rows being sorted by the values of one or more columns. The sort criteria does not have to be included in the result set (restrictions apply for SELECT DISTINCT, GROUP BY, UNION [DISTINCT], EXCEPT [DISTINCT] and INTERSECT [DISTINCT].)
In particular, it is a component of Structured Query Language (SQL). Data Control Language is one of the logical group in SQL Commands. SQL [1] is the standard language for relational database management systems. SQL statements are used to perform tasks such as insert data to a database, delete or update data in a database, or retrieve data ...
The OFFSET clause specifies the number of rows to skip before starting to return data. The FETCH FIRST clause specifies the number of rows to return. Some SQL databases instead have non-standard alternatives, e.g. LIMIT, TOP or ROWNUM. The clauses of a query have a particular order of execution, [5] which is denoted by the number on the right ...
The idea was that you could do a JOIN to the DUAL table and create two rows in the result for every one row in your table. Then, by using GROUP BY, the resulting join could be summarized to show the amount of storage for the DATA extent and for the INDEX extent(s). The name, DUAL, seemed apt for the process of creating a pair of rows from just one.