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2. SQL syntax - Wikipedia

   en.wikipedia.org/wiki/SQL_syntax

   Additionally, because SQL operators return Unknown when comparing anything with Null directly, SQL provides two Null-specific comparison predicates: IS NULL and IS NOT NULL test whether data is or is not Null. [8] SQL does not explicitly support universal quantification, and must work it out as a negated existential quantification.

3. Set operations (SQL) - Wikipedia

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

   Set operations in SQL is a type of operations which allow the results of multiple queries to be combined into a single result set. [1] Set operators in SQL include UNION, INTERSECT, and EXCEPT, which mathematically correspond to the concepts of union, intersection and set difference.

4. Null (SQL) - Wikipedia

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

   Basic SQL comparison operators always return Unknown when comparing anything with Null, so the SQL standard provides for two special Null-specific comparison predicates. The IS NULL and IS NOT NULL predicates (which use a postfix syntax) test whether data is, or is not, Null.

5. Ternary conditional operator - Wikipedia

   en.wikipedia.org/wiki/Ternary_conditional_operator

   The detailed semantics of "the" ternary operator as well as its syntax differs significantly from language to language. A top level distinction from one language to another is whether the expressions permit side effects (as in most procedural languages) and whether the language provides short-circuit evaluation semantics, whereby only the selected expression is evaluated (most standard ...

6. Relational algebra - Wikipedia

   en.wikipedia.org/wiki/Relational_algebra

   The relational algebra uses set union, set difference, and Cartesian product from set theory, and adds additional constraints to these operators to create new ones.. For set union and set difference, the two relations involved must be union-compatible—that is, the two relations must have the same set of attributes.

7. Transact-SQL - Wikipedia

   en.wikipedia.org/wiki/Transact-SQL

   Transact-SQL is central to using Microsoft SQL Server. All applications that communicate with an instance of SQL Server do so by sending Transact-SQL statements to the server, regardless of the user interface of the application. Stored procedures in SQL Server are executable server-side routines. The advantage of stored procedures is the ...

8. Comparison of relational database management systems - Wikipedia

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

   An SQL schema is simply a namespace within a database; things within this namespace are addressed using the member operator dot ". This seems to be a universal among all of the implementations. A true fully (database, schema, and table) qualified query is exemplified as such: SELECT * FROM database . schema . table

9. Where (SQL) - Wikipedia

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

   A WHERE clause in SQL specifies that a SQL Data Manipulation Language (DML) statement should only affect rows that meet specified criteria. The criteria are expressed in the form of predicates. WHERE clauses are not mandatory clauses of SQL DML statements, but can be used to limit the number of rows affected by a SQL DML statement or returned ...