Learning MySQL By Example

1. How to Retrieve Data From a Single Table

1.1. The Five Clauses of the SELECT Statement

1.2. Column Specifications

1.3. LIKE and REGEXP Operators

1.4. Arithmetic Operators

1.5. Column Aliases

1.6. Comparison Operators

1.7. IS NULL, BETWEEN, IN Operators

1.8. AND, OR, NOT Logical Operators

1.9. DISTINCT Clause

2. How to Retrieve Data from Multiple Tables

2.1. The JOIN Clause

2.2. Joining More Than Two Tables

2.3. The OUTER JOIN Clause

2.4. How to Code a UNION

3. Using Functions

3.1. Date Functions

3.2. Numeric Functions

3.3. String Functions

4. How to Insert, Update, Delete Data in Tables

4.1. The INSERT Clause With a Column List

4.2. The INSERT Clause Without a Column List

4.4. The UPDATE Clause With a Column List

4.4. The DELETE Clause

5. Summary Queries and Aggregate Functions

5.1. Aggregate Functions

5.2. Grouping Data

5.3. Simple GROUP BY Query

5.4. Improving the GROUP BY Query

5.5. Using the HAVING Clause

5.5. Using the HAVING and WHERE Clauses Together

5.6. COUNT(column_name) and COUNT(*)

5.7. Using the DISTINCT Statement

6. Working With Subqueries

6.1. The Subquery In a SELECT Statement

6.2. The Subquery in an UPDATE statement

6.3. Create a Duplicate Table From An Existing Table

6.4. The Subquery In a Delete Statement

7.1. SQL View Explained

7.2. Benefits of Using Views

7.3. Views That Allow UPDATE Statements

8.2. Clustered vs. Non-clustered Indexes

8.3. Create an Index in Workbench Using an ERD

8.4. How to Manually Add an Index to an Existing Table

8.1

SQL Indexes Explained

SQL Indexes

You can create SQL indexes from single or multiple columns.
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.
MySQL automatically creates indexes for primary and foreign keys significantly speeding up join performance.
You should only create indexes on columns used in a join or search because the RDMS must update an index every time you execute an INSERT, UPDATE, or DELETE.

When to Create an Index

When a column is used frequently in a search or a join.
When a column contains a large number of distinct values.
When the column is updated infrequently

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