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MSDN documentation on UNION in Transact-SQL for SQL Server; Naming of select list items in set operations; UNION in MySQL with Examples; UNION in MySQL; UNION Clause in PostgreSQL; SQL UNION and UNION ALL; Sort order within UNION statement; Designing a data flow that loads a warehouse table; Oracle 11g documentation for UNION (ALL), INTERSECT ...
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 ]
SQL includes operators and functions for calculating values on stored values. SQL allows the use of expressions in the select list to project data, as in the following example, which returns a list of books that cost more than 100.00 with an additional sales_tax column containing a sales tax figure calculated at 6% of the price.
Title Authors ----- ----- SQL Examples and Guide 4 The Joy of SQL 1 An Introduction to SQL 2 Pitfalls of SQL 1 Under the precondition that isbn is the only common column name of the two tables and that a column named title only exists in the Book table, one could re-write the query above in the following form:
The natural join can be simulated with Codd's primitives as follows. Let c 1, ..., c m be the attribute names common to R and S, r 1, ..., r n be the attribute names unique to R and let s 1, ..., s k be the attributes unique to S. Furthermore, assume that the attribute names x 1, ..., x m are neither in R nor in S.
High-cardinality column values are typically identification numbers, email addresses, or user names. An example of a data table column with high-cardinality would be a USERS table with a column named USER_ID. This column would contain unique values of 1-n. Each time a new user is created in the USERS table, a new number would be created in the ...
SQL statements are used to perform tasks such as insert data to a database, delete or update data in a database, or retrieve data from a database. Though database systems use SQL, they also have their own additional proprietary extensions that are usually only used on their system.
In a SQL database query, a correlated subquery (also known as a synchronized subquery) is a subquery (a query nested inside another query) that uses values from the outer query. This can have major impact on performance because the correlated subquery might get recomputed every time for each row of the outer query is processed.