• Learning MySQL By Example
  • Introduction
  • 1. How to Retrieve Data From a Single Table
  • 2. How to Retrieve Data from Multiple Tables
  • 3. Using Functions
  • 4. How to Insert, Update, Delete Data in Tables
  • 5. Summary Queries and Aggregate Functions
  • 6. Working With Subqueries
  • 7. SQL Views
  • 8. SQL Indexes
  • Glossary
  • Index
  • Download
  • Translations
  • Glossary

    Aggregate Function

    Performs an operation on a set of records in a column and returns a single value.

    Arithmetic Operators

    Arithmetic operators ARE: * (multiplication), / (division), DIV (integer division), % (MOD) or remainder, + (addition), - (subtraction). These operators can be used in the SELECT, WHERE, and ORDER BY clauses. Operators are evaluated in the same way as arithmetic in other contexts.

    AVG function

    Returns the average of the non-null columns in the expression.

    BETWEEN operator

    The BETWEEN operator is similar to >= and <=. BETWEEN includes everything between the two values indicated. BETWEEN works with both text and number.

    CEILING function

    Returns the next highest whole number no matter what the decimal point.

    Column Aliases

    A column alias provides a way to create a clean or more descriptive header for a results set. A column alias cannot be used in a SELECT, WHERE, GROUP BY or HAVING clause due to the order of execution. You must refer to the original column name.

    Column Specifications

    A column specification may be derived from a base table. Or it my be a calculated value as a result of an arithmetic expression or a function.

    Comparison Operators

    The comparison operators are = (equals), < (less than), > (greater than), <= (less than or equal to), >=, <> (not equal), != (not equal). Comparison operators compare two expressions. The result of a comparison results to true or false. Comparison operators are not case sensitive and are used with text and dates as well as numbers.

    Compound condition

    When more than one logical operator (AND, OR, NOT) is used in the WHERE clause.

    CONCAT function

    Combines a list of strings into a single string.

    COUNT function

    The number of the non-null columns in the expression.

    CURRENT_DATE function

    Returns current local date.

    CURRENT_TIME function

    Returns current local time

    DATE function

    Extracts the date from date/time input. If time is included it is dropped.

    DELETE clause

    SQL clause that deletes data from a table.

    DISTINCT clause

    The DISTINCT clause removes duplicate rows from a query.

    FLOOR function

    Returns the next lowest whole number no matter what the decimal point.

    FROM clause

    Specifies the base table(s) from which results will be retrieved.

    GROUP BY clause

    Groups rows of a result set based on columns or expressions separated by commas.

    HAVING clause

    The HAVING CLAUSE allows you to use an aggregate function as a filter. This is not allowed in a WHERE clause.

    IN operator

    The IN operator tests whether an expression is equal to a value or values in a list of expressions. The order of the items in the list does not matter. You can use the NOT operator to test for items not in the list. The IN clause may be used with a subquery.


    A SQL index is like the index of a book. It speeds up the retrieval of a record. The relational database management system (RDBMS) can retrieve a record with the index key instead of having to perform a table scan.

    INSERT clause

    SQL Clause used to insert data into a table.

    IS NULL function

    Null values indicate an unknown or non-existent value and is different from an empty string (‘ ‘). To test for a null value you use the IS NULL clause. The test for a value use IS NOT NULL clause

    JOIN (OUTER) clause

    An outer join will return all the rows from one table and only the rows from the other table that match the join condition

    JOIN clause

    A JOIN clause allows you to access data from two or more tables in a query.

    LEFT function

    Returns a substring starting from the left side of the string.

    LIKE operator

    The LIKE keyword is used with the WHERE clause. The LIKE keyword and can use two symbols as wildcards. The percent ( % ) symbol matches any number of characters and the underscore ( _ ) matches a single character.

    LIMIT clause

    Specifies the number of rows to be returned.

    Logical Operators: AND, OR, NOT

    Logical operators are used in the WHERE clause You may use multiple logical operators in a WHERE clause to create a compound condition. The order of evaluation when multiple operators are used is shown in the table above.

    LTRIM function

    Removes leading spaces from a string.

    MIN function

    The lowest value off the non-null columns in the expression

    NOW function

    Returns current local date and time.

    ORDER BY clause

    SQL clause that orders a result set.

    REGEXP operator

    REGEXP operator allows you to do more complex pattern matching than a LIKE keyword/ Some version of REGEXP exists in many computer languages. Refer to the “LIKE and REGEXP” handout for a full list of examples.

    RIGHT function

    Returns a substring starting from the right side of the string.

    ROUND function

    Rounds to the decimal specified.

    RTRIM function

    Removes trailing spaces from a string.

    SELECT clause

    Specifies the columns that will appear in a SQL query result set.


    A subquery is a SELECT statement coded within another SELECT statement.

    SUM function

    The total of the non-null columns in the expression.

    Summary Query

    A query that uses at least one aggregate function.

    TRIM function

    Removes leading and trailing spaces from a string.

    TRUNCATE function

    Returns the number truncated to the precision specified.

    UNION clause

    A UNION combines the results of two or more queries into a single result set.

    UPDATE clause

    SQL clause that updates data in a table.

    UTC_DATE function

    Returns current UTC date.

    UTC_time function

    Returns current UTC time.


    A SQL view is a SELECT statement that is stored as a database object.

    WHERE function

    Specifies any conditions for the results set (filter).

    This content is provided to you freely by BYU-I Books.

    Access it online or download it at https://books.byui.edu/learning_mysql/glossary.