The Data Control Language (DCL) has four commands that are COMMIT, ROLLBACK, GRANT, and REVOKE. These commands are used to protect the database from harm, both accidental or intentional.
it all comes down to the database storage and efficiency. choosing the best matching data types for each coloumn in your table will reduce the size of table and make operations on your data faster.
A table can have one of the following index configurations:
- No indexes
- A clustered index
- A clustered index and many nonclustered indexes
- A nonclustered index
- Many nonclustered indexes
Because its a waste of space. char or text will use specific amount of space and not more than 256 characters. But a BLOB will use so much of space. So there is a possibility to a face out of space issue in future.
To be in first normal form (1NF), a table must have the following qualities:
- The table is two-dimensional, with rows and columns
- Each row contains data that pertains to some thing or portion of a thing.
- Each column contains data for a single attribute of the thing it’s describing.
- Each cell (intersection of a row and a column) of the table must have only a single value
- Entries in any column must all be of the same kind. If, for example, the entry in one row of a column contains an employee name, all the other rows must contain employee names in that column, too.
- Each column must have a unique name
- No two rows may be identical (that is, each row must be unique).
- The order of the columns and the order of the rows are not significant.
The SELECT clause merely tells the database what data you want to see. The FROM clause tells the database where to get the data.
They are sorted as ASCII characters. This means that numbers would be ordered like this: 1, 12, 2, 222, 22222, 3, 33.
Yes. Multiple conditions can be specified in the WHERE clause of SELECT, INSERT, UPDATE, and DELETE statements. Multiple conditions are used with the operators AND and OR,
You receive a Cartesian product by not joining the tables and this is also called a cross join.
No. A column with a large percentage of NULLvalues should not be indexed because the speed of accessing these rows degrades when the value of a large percentage of rows is the same.
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