(6) Fundamentals of SQL Flashcards
Alias
An alternative name for a column or a table in a SQL statement.
ALTER TABLE
The SQL command used to make changes to table structure. When the command is followed by a keyword (ADD or MODIFY), it adds a column or changes column characteristics.
AND
The SQL logical operator used to link multiple conditions expressions in a WHERE or HAVING clause. It requires that all conditional expressions evaluate to true.
AVG
A SQL aggregate fusion that outputs the mean average for a specified column or expression.
BETWEEN
In SQL, a special comparison operator used to check whether a value is within a range of specified values.
Boolean algebra
A branch of mathematics that uses logical operators OR, AND, and NOT.
Cascading order sequence
A nested ordering for a set of rows, such as a list in which all last names are alphabetically ordered and, within the last names, all first names are ordered.
COMMIT
The SQL command that permanently writes data changes to a database.
COUNT
A SQL aggregate function that outputs the number of rows containing not null values for a given column or expression, sometimes used in conjunction with the DISTINCT clause.
CREATE INDEX
A SQL command that creates indexes on the basis of a selected attribute or attributes.
CREATE TABLE
A SQL command that creates a table’s structures using the characteristics and attributes given.
DELETE
A SQL command that allows data rows to be deleted from a table.
DISTINCT
A SQL clause that produces only a list of values that are different from one another.
DROP INDEX
A SQL command used to delete database objects such as table’s, views, indexes, and users.
DROP TABLE
A SQL command used to delete database objects such as table’s, views, indexes, and users.
EXISTS
In SQL, a comparison operator that checks whether a sub query returns any rows.
FROM
A SQL clause that specifies the table or table’s from which data is to be retrieved.
GROUP BY
A SQL clause used to create frequency distributions when combined with any of the aggregate functions in a SELECT statement.
HAVING
A clause applied to the output of a GROUP BY operation to restrict selected rows.
IN
In SQL, a comparison operator used to check whether a value is among a list of specified values.
inner query
A query that is embedded or nested inside another query.
INSERT
A SQL command that allows the insertion of one or more data rows into a table.
International Organization for Standardization (ISO)
An organization formed to develop standards for diverse network systems.
IS NULL
In SQL, a comparison operator used to check whether an attribute has a value.
LIKE
In SQL, a comparison used to check whether an attribute’s text value matches a specified string pattern.
MAX
A SQL aggregate function that yields the maximum attribute in a given column.
MIN
A SQL aggregate function that yields the minimum attribute in a given column.
Nested query
In SQL, a query that is embedded in another query.
NOT
A SQL logical operator that negates a given predicate.
OR
the SQL logical operator used to link multiple conditional expressions in a WHERE or HAVING clause. It requires only one of the conditional expressions to be true.
ORDER BY
A SQL clause that is useful for ordering the output of a SELECT query (for example, in ascending or descending order).
ROLLBACK
A SQL command that restores the database table contents to the condition that existed after the last COMMIT statement.
Rules of precedence
Basic algebra is rules that specify the order in which operations are performed. For example, operations within parentheses are executed first, so in the equation 2 + (3 5), the multiplication is calculated first, making the correct answer 17.
Subquery
A query that is embedded (or nested) inside another query.
SUM
A SQL aggregate function that yields the sum of all values for a given column or expression.
UPDATE
A SQL command that allows attribute values to be changed in one or more rows of a table.
WHERE
A SQL clause that adds conditional restrictions to a SELECT statement that limit the rows returned by the query.
Wildcard character
A symbol that can be used as a general substitute for: (1) all columns in a table (*) when used in an attribute list of a SELECT statement or, (2) zero or more characters in a SQL LIKE clause condition (% and _ ).
