SUM, AVG, MIN, and MAX can only be used with numeric columns.

More Questions from Introduction to SQL

• The HAVING clause acts like a WHERE clause, but it identifies groups that meet a criterion, rather than rows.
• 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.

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