Update introduction.md

sql/introduction.md

@@ -11,112 +11,112 @@ A database row represents a single, implicitly structured data record in a table
 ### column
 A database column is a set of data values of a particular simple type, one value for each row of the database. A column may contain text values, numbers, or even pointers to files in the operating system.
 
-### primary key
-A primary key, sometimes labeled as the unique identifier, is a specific choice of a set of columns that uniquely identify a row in a relational table. Simply put, a primary key is the attributes which identify a record.
+### CREATE TABLE
+`CREATE TABLE` creates a new table in the database. It allows you to specify the name of the table and the name of each column in the table.
 
 ### ALTER TABLE
 `ALTER TABLE` lets you add columns to a table in a database.
 
+### PRIMARY KEY
+A primary key, sometimes labeled as the unique identifier, is a specific choice of a set of columns that uniquely identify a row in a relational table. Simply put, a primary key is the attributes which identify a record.
+
+### INSERT
+`INSERT` statements are used to add a new row to a table.
+
 ### CASE
 `CASE` statements are used to create different outputs (usually in the `SELECT` statement). It is SQL’s way of handling if-then logic.
 
-### CREATE TABLE
-`CREATE TABLE` creates a new table in the database. It allows you to specify the name of the table and the name of each column in the table.
-
 ### DELETE
 `DELETE` statements are used to remove rows from a table.
 
 ### INNER JOIN
 An INNER JOIN will combine rows from different tables if the *join condition* is true.
 
-### INSERT
-`INSERT` statements are used to add a new row to a table.
-
-### IS NULL / IS NOT NULL
-`IS NULL` and `IS NOT NULL` are operators used with the `WHERE` clause to test for empty values.
-
 ### OUTER JOIN
 An outer join will combine rows from different tables even if the join condition is not met. Every row in the *left* table is returned in the result set, and if the join condition is not met, then `NULL` values are used to fill in the columns from the *right* table.
 
-### SELECT DISTINCT
-`SELECT DISTINCT` specifies that the statement is going to be a query that returns unique values in the specified column(s).
-
 ### UPDATE
 `UPDATE` statements allow you to edit rows in a table.
 
 ### WITH
 `WITH` clause lets you store the result of a query in a temporary table using an alias. You can also define multiple temporary tables using a comma and with one instance of the `WITH` keyword.
 The `WITH` clause is also known as common table expression (CTE) and subquery factoring.
 
-### AND
-The `AND` operator allows multiple conditions to be combined. Records must match both conditions that are joined by `AND` to be included in the result set.
-
 ### AS
 Columns or tables in SQL can be *aliased* using the `AS` clause. This allows columns or tables to be specifically renamed in the returned result set.
 
-### OR
-The `OR` operator allows multiple conditions to be combined. Records matching either condition joined by the `OR` are included in the result set.
-
-### %
-The `%` wildcard can be used in a `LIKE` operator pattern to match zero or more unspecified character(s).
-
 ### SELECT
 The `SELECT *` statement returns all columns from the provided table in the result set.
 
-### _
-The `_` wildcard can be used in a `LIKE` operator pattern to match any single unspecified character.
+### DISTINCT
+Unique values of a column can be selected using a `DISTINCT` query.
 
-### ORDER BY
-The `ORDER BY` clause can be used to sort the result set by a particular column either alphabetically or numerically. It can be ordered in ascending (default) or descending order with `ASC`/`DESC`.
+### SELECT DISTINCT
+`SELECT DISTINCT` specifies that the statement is going to be a query that returns unique values in the specified column(s).
+
+### WHERE
+The `WHERE` clause is used to filter records (rows) that match a certain condition.
 
 ### LIKE
 The `LIKE` operator can be used inside of a `WHERE` clause to match a specified pattern.
 
-### DISTINCT
-Unique values of a column can be selected using a `DISTINCT` query.
+### _
+The `_` wildcard can be used in a `LIKE` operator pattern to match any single unspecified character.
+
+### %
+The `%` wildcard can be used in a `LIKE` operator pattern to match zero or more unspecified character(s).
 
 ### BETWEEN
 The `BETWEEN` operator can be used to filter by a *range* of values. The range of values can be text, numbers or date data.
 
+### AND
+The `AND` operator allows multiple conditions to be combined. Records must match both conditions that are joined by `AND` to be included in the result set.
+
+### OR
+The `OR` operator allows multiple conditions to be combined. Records matching either condition joined by the `OR` are included in the result set.
+
+### IS NULL / IS NOT NULL
+`IS NULL` and `IS NOT NULL` are operators used with the `WHERE` clause to test for empty values.
+
+### ORDER BY
+The `ORDER BY` clause can be used to sort the result set by a particular column either alphabetically or numerically. It can be ordered in ascending (default) or descending order with `ASC`/`DESC`.
+
 ### LIMIT
 The `LIMIT` clause is used to narrow, or *limit*, a result set to the specified number of rows.
 
 ### NULL
 Column values in SQL records can be `NULL`, or have no value. These records can be matched (or not matched) using the `IS NULL` and `IS NOT NULL` operators in combination with the `WHERE` clause.
 
-### WHERE
-The `WHERE` clause is used to filter records (rows) that match a certain condition.
+### Aggregate Functions
+Aggregate functions perform a calculation on a set of values and return a single value:
 
-### Column References
-The `GROUP BY` and `ORDER BY` clauses can reference the selected columns by number in which they appear in the `SELECT` statement.
+### COUNT()
+The `COUNT()` aggregate function in SQL returns the total number of rows that match the specified criteria.
 
 ### SUM()
 The `SUM()` aggregate function takes the name of a column as an argument and returns the sum of all the value in that column.
 
 ### MAX()
 The `MAX()` aggregate function in SQL takes the name of a column as an argument and returns the largest value in a column.
 
-### COUNT()
-The `COUNT()` aggregate function in SQL returns the total number of rows that match the specified criteria.
-
-### GROUP BY
-The `GROUP BY` clause will group records in a result set by identical values in one or more columns. It is often used in combination with aggregate functions to query information of similar records. The `GROUP BY` clause can come after `FROM` or `WHERE` but must come before any `ORDER BY` or `LIMIT` clause.
-
 ### MIN()
 The `MIN()` aggregate function in SQL returns the smallest value in a column.
 
 ### AVG()
 The `AVG()` aggregate function returns the average value in a column.
 
+### GROUP BY
+The `GROUP BY` clause will group records in a result set by identical values in one or more columns. It is often used in combination with aggregate functions to query information of similar records. The `GROUP BY` clause can come after `FROM` or `WHERE` but must come before any `ORDER BY` or `LIMIT` clause.
+
 ### HAVING
 The `HAVING` clause is used to further filter the result set groups provided by the `GROUP BY` clause. `HAVING` is often used with aggregate functions to filter the result set groups based on an aggregate property.
 
-### Aggregate Functions
-Aggregate functions perform a calculation on a set of values and return a single value:
-
 ### ROUND()
 The `ROUND()` function will round a number value to a specified number of places. It takes two arguments: a number, and a number of decimal places. It can be combined with other aggregate functions
 
+### Column References
+The `GROUP BY` and `ORDER BY` clauses can reference the selected columns by number in which they appear in the `SELECT` statement.
+
 ## References:
 - https://www.codecademy.com/articles/sql-commands