SQL Working With Dates
SQL Dates
The most difficult part when working with dates is to be sure that the format of the date you are trying to insert, matches the format of the date column in the database.
As long as your data contains only the date portion, your queries will work as expected. However, if a time portion is involved, it gets more complicated.SQL Date Data Types
MySQL comes with the following data types for storing a date or a date/time value in the database:- DATE - format YYYY-MM-DD
- DATETIME - format: YYYY-MM-DD HH:MI:SS
- TIMESTAMP - format: YYYY-MM-DD HH:MI:SS
- YEAR - format YYYY or YY
- DATE - format YYYY-MM-DD
- DATETIME - format: YYYY-MM-DD HH:MI:SS
- SMALLDATETIME - format: YYYY-MM-DD HH:MI:SS
- TIMESTAMP - format: a unique number
SQL Working with Dates
You can compare two dates easily if there is no time component involved!
Assume we have the following "Orders" table:| OrderId | ProductName | OrderDate |
|---|---|---|
| 1 | Geitost | 2008-11-11 |
| 2 | Camembert Pierrot | 2008-11-09 |
| 3 | Mozzarella di Giovanni | 2008-11-11 |
| 4 | Mascarpone Fabioli | 2008-10-29 |
We use the following SELECT statement:
SELECT * FROM Orders WHERE OrderDate='2008-11-11'The result-set will look like this:| OrderId | ProductName | OrderDate |
|---|---|---|
| 1 | Geitost | 2008-11-11 |
| 3 | Mozzarella di Giovanni | 2008-11-11 |
| OrderId | ProductName | OrderDate |
|---|---|---|
| 1 | Geitost | 2008-11-11 13:23:44 |
| 2 | Camembert Pierrot | 2008-11-09 15:45:21 |
| 3 | Mozzarella di Giovanni | 2008-11-11 11:12:01 |
| 4 | Mascarpone Fabioli | 2008-10-29 14:56:59 |
SELECT * FROM Orders WHERE OrderDate='2008-11-11'we will get no result! This is because the query is looking only for dates with no time portion.Tip: To keep your queries simple and easy to maintain, do not allow time components in your dates!
