Thread: SQL issues

Hi. I am learning SQL. I have some issue while learning SQL

• difference between char and varchar in SQL server 2005

• what is composite key and candidate key

• how to calculate difference between two dates

If you have any detailed info related this topic then let me know that it is highly appreciated.

• Char data type is used to save fixed length character value and varchar is used to store variable length character value.

• Combination of multiple fields will create the uniqueness is called composite key.

• A field has the capability to become a primary key is known as candidate key

• Using DATEDIFF function
For example: SELECT DATEDIFF(dd,"16 june 2010","18 july 2010")

Thanks for giving such a nice information…….