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An SQL UPDATE statement changes the data of one or more records in a table. Either all the rows can be updated, or a subset may be chosen using a condition. The UPDATE statement has the following form: [1] UPDATE table_name SET column_name = value [, column_name = value ...] [WHERE condition]
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 .
Additionally there is a single-row version, UPDATE OR INSERT INTO tablename (columns) VALUES (values) [MATCHING (columns)], but the latter does not give you the option to take different actions on insert versus update (e.g. setting a new sequence value only for new rows, not for existing ones.)
The WHERE clause eliminates all rows from the result set where the comparison predicate does not evaluate to True. The GROUP BY clause projects rows having common values into a smaller set of rows. [clarification needed] GROUP BY is often used in conjunction with SQL aggregation functions or to eliminate duplicate rows from a result set.
A cursor is a pointer to a private SQL area that stores information coming from a SELECT or data manipulation language (DML) statement (INSERT, UPDATE, DELETE, or MERGE). A cursor holds the rows (one or more) returned by a SQL statement. The set of rows the cursor holds is referred to as the active set. [12] A cursor can be explicit or implicit ...
In relational databases, the information schema (information_schema) is an ANSI-standard set of read-only views that provide information about all of the tables, views, columns, and procedures in a database. [1] It can be used as a source of the information that some databases make available through non-standard commands, such as:
A common table expression, or CTE, (in SQL) is a temporary named result set, derived from a simple query and defined within the execution scope of a SELECT, INSERT, UPDATE, or DELETE statement. CTEs can be thought of as alternatives to derived tables ( subquery ), views , and inline user-defined functions.
In the context of Oracle Databases, a schema object is a logical data storage structure. [4] An Oracle database associates a separate schema with each database user. [5] A schema comprises a collection of schema objects. Examples of schema objects include: tables; views; sequences; synonyms; indexes; clusters; database links; snapshots ...