No edit summary |
No edit summary |
||
Line 47: | Line 47: | ||
SELECT COUNT(*) | SELECT COUNT(*) | ||
FROM people; | FROM people; | ||
Placing a column in the count command will count all the non missing values. | Placing a column in the count command will count all the non missing values. | ||
This will count the number of birth dates present in the people table | This will count the number of birth dates present in the people table | ||
SELECT COUNT(birthdate) | SELECT COUNT(birthdate) | ||
FROM people; | FROM people; | ||
To count the number of distinct values, the following can be used | To count the number of distinct values, the following can be used | ||
SELECT COUNT(DISTINCT birthdate) | SELECT COUNT(DISTINCT birthdate) | ||
FROM people; | FROM people; | ||
</nowiki> | </nowiki> |
Revision as of 02:40, 12 September 2023
Below I have listed the most common commands that I am using when acquiring data from a database
Selecting a single Column from a table:
This will select the column "Name" from the "People" Table. SELECT name FROM people;
Selecting multiple columns from a table:
This will select the Name and Birthrate column from the people table. SELECT name, birthdate FROM people;
This will select all columns from a table. SELECT * FROM people;
This will select 10 rows with all columns from a table. SELECT * FROM people LIMIT 10;
This will select 10 rows with all columns from a table. SELECT * FROM people LIMIT 10;
Selecting all unique values from a column:
This will select all the unique values in the language column from the films Table. SELECT DISTINCT language FROM films;
Counting in a table:
This will count all the rows in the people table. SELECT COUNT(*) FROM people; Placing a column in the count command will count all the non missing values. This will count the number of birth dates present in the people table SELECT COUNT(birthdate) FROM people; To count the number of distinct values, the following can be used SELECT COUNT(DISTINCT birthdate) FROM people;