Mega Code Archive
Total number of the table vs unique values count
<![CDATA[
mysql>
mysql> CREATE TABLE IF NOT EXISTS rings
-> (
-> id INT AUTO_INCREMENT PRIMARY KEY,
-> stone CHAR(10) NOT NULL,
-> price DECIMAL(3,2) NOT NULL
-> );
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> INSERT INTO rings (stone, price) VALUES ("Ruby", 40.00);
Query OK, 1 row affected, 1 warning (0.00 sec)
mysql> INSERT INTO rings (stone, price) VALUES ("Emerald", 40.00);
Query OK, 1 row affected, 1 warning (0.00 sec)
mysql> INSERT INTO rings (stone, price) VALUES ("Diamond", 60.00);
Query OK, 1 row affected, 1 warning (0.00 sec)
mysql> INSERT INTO rings (stone, price) VALUES ("Diamond", 50.00);
Query OK, 1 row affected, 1 warning (0.00 sec)
mysql> INSERT INTO rings (stone, price) VALUES ("Garnet", 40.00);
Query OK, 1 row affected, 1 warning (0.00 sec)
mysql>
mysql> # display all data in the "rings" table
mysql> SELECT * FROM rings;
+----+---------+-------+
| id | stone | price |
+----+---------+-------+
| 1 | Ruby | 9.99 |
| 2 | Emerald | 9.99 |
| 3 | Diamond | 9.99 |
| 4 | Diamond | 9.99 |
| 5 | Garnet | 9.99 |
+----+---------+-------+
5 rows in set (0.00 sec)
mysql>
mysql> # get the total number of rows
mysql> SELECT COUNT(price) AS num_prices
-> FROM rings;
+------------+
| num_prices |
+------------+
| 5 |
+------------+
1 row in set (0.00 sec)
mysql>
mysql> # get the number of unique rows
mysql> SELECT COUNT(DISTINCT price) AS num_distinct_prices
-> FROM rings;
+---------------------+
| num_distinct_prices |
+---------------------+
| 1 |
+---------------------+
1 row in set (0.00 sec)
mysql>
mysql> # get all the unique stone values
mysql> SELECT DISTINCT stone AS unique_stone_names FROM rings;
+--------------------+
| unique_stone_names |
+--------------------+
| Ruby |
| Emerald |
| Diamond |
| Garnet |
+--------------------+
4 rows in set (0.00 sec)
mysql>
mysql> # delete this sample table
mysql> DROP TABLE IF EXISTS rings;
Query OK, 0 rows affected (0.00 sec)
mysql>
]]>