Introduction to SQL Questions

• The wildcard asterisk (*) is the SQL-92 standard for indicating "any sequence of characters."
• Indexes can usually be created for both primary and secondary keys.
• Scalar aggregate are multiple values returned from an SQL query that includes an aggregate function.
• Data manipulation language (DML) commands are used to define a database, including creating, altering, and dropping tables and establishing constraints.
• DISTINCT and its counterpart, ALL, can be used more than once in a SELECT statement.
• SELECT DISTINCT is used if a user wishes to see duplicate columns in a query.
• The SQL statement: SELECT Name, COUNT(*) FROM NAME_TABLE; counts the number of name rows and displays this total in a table with a single row and a single column.
• The qualifier DISTINCT must be used in an SQL statement when we want to eliminate duplicate rows.
• There is an equivalent join expression that can be substituted for all subquery expressions.
• The ADD command is used to enter one row of data or to add multiple rows as a result of a query.
• The result of every SQL query is a table.
• The rows of the result relation produced by a SELECT statement can be sorted, but only by one column.
• The SQL keyword GROUP BY instructs the DBMS to group together those rows that have the same value in a column.
• ORDER BY can be combined with the SELECT statements.
• Each index consumes extra storage space and also requires overhead maintenance time whenever indexed data change value.
• To establish a range of values, < and > can be used.
• SQL provides the AS keyword, which can be used to assign meaningful column names to the results of queries using the SQL built-in functions.
• The condition in a WHERE clause can refer to only one value.
• If you are going to use a combination of three or more AND and OR conditions, it is often easier to use the NOT and NOT IN operators.
• The keyword BETWEEN can be used in a WHERE clause to refer to a range of values.