SQL SELECT

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Exercises

For these exercises, assume we have a table called Users with the following columns:

Table Users

Column Name

First_Name

Last_Name

Birth_Date

Gender

Date_Joined

1. Which of the following SQL statement is incorrect? (There can be more than one answer)
a) SELECT * FROM Users;
b) SELECT First_Name, Gender, Last_Name FROM Users;
c) SELECT First_Name, Last_Name Users;
d) SELECT All FROM Users;

2. (True Or False) In SQL, the order of the columns in a SELECT statement must be the same as the order of the columns in the underlying table. For example, in the table Users, you must select First_Name before Last_Name.

3. (True Or False) The following two SQL statements are equivalent:
a) Select * From Users;
b) SELECT * FROM Users;

1. c), d).

2. False. The order of columns in a table has no relationship to the order of columns in a SELECT statement.

3. True. SQL keywords such as SELECT and FROM are not case-sensitive.

Next: SQL DISTINCT

This page was last updated on October 11, 2024.

SQL > SQL Commands > Select

The SELECT statement in SQL is used to retrieve data from a relational database.

Syntax

Number of Columns	SQL Syntax
1	SELECT "column_name" FROM "table_name";
More Than 1	SELECT "column_name1"[, "column_name2"] FROM "table_name";
All	SELECT * FROM "table_name";

"table_name" is the name of the table where data is stored, and "column_name" is the name of the column containing the data to be retrieved.

To select more than one column, add a comma to the name of the previous column, and then add the column name. If you are selecting three columns, the syntax will be,

SELECT "column_name1", "column_name2", "column_name3" FROM "table_name";

Note there is no comma after the last column selected.

Special Case

Note that the FROM keyword appears in all of the scenarios above, since the FROM keyword is used to indicate which table(s) one is retrieving the data from. There is one special case where FROM does not exist, and that is when you are doing a mathematical operation. In this case, the syntax is simply,

SELECT [Math Operation];

Examples

We will provide examples for each of the following four use cases:

Retrieve one column
Retrieve multiple columns
Retrieve all columns
Do math operation

Let's use the following table to illustrate all three cases:

Table Store_Information

Store_Name Sales Txn_Date

Los Angeles 1500 Jan-05-1999

San Diego 250 Jan-07-1999

Los Angeles 300 Jan-08-1999

Boston 700 Jan-08-1999

Example 1: Select one column

To select a single column, we specify the column name between SELECT and FROM as follows:

SELECT Store_Name FROM Store_Information;

Result:

Store_Name

Los Angeles

San Diego

Los Angeles

Boston

Example 2: Select multiple columns

We can use the SELECT statement to retrieve more than one column. To select Store_Name and Sales columns from Store_Information, we use the following SQL:

SELECT Store_Name, Sales FROM Store_Information;

Result:

Store_Name Sales

Los Angeles 1500

San Diego 250

Los Angeles 300

Boston 700

Example 3: Select all columns

There are two ways to select all columns from a table. The first is to list the column name of each column. The second, and the easier, way is to use the symbol *. For example, to select all columns from Store_Information, we issue the following SQL:

SELECT * FROM Store_Information;

Result:

Store_Name Sales Txn_Date

Los Angeles 1500 Jan-05-1999

San Diego 250 Jan-07-1999

Los Angeles 300 Jan-08-1999

Boston 700 Jan-08-1999

Example 4: Math operation

If we want to use the SELECT statement to calculate 2+3, we issue the following SQL:

SELECT 2+3;

Result:

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