This table contains only two columns, ID and Name. If the null-ability is not specified while defining the column, it will accept the NULL value by default:. The last insert operation will fail, as we only provide the INSERT statement with a value for the Name column, without providing value for the ID column that is mandatory and cannot be assigned NULL value, as shown in the error message below:.
Checking the inserted data, you will see that only two records are inserted and the missing value for the Name column in the second INSERT statement will be NULL, which is the default value, as shown in the result below:. You will see that the command will fail, as it will check the existing values of the Name column for NULL values first before creating the constraint, as shown in the error message below:.
If you try to create the Constraints in SQL again, it will be created successfully as shown below:. Beside each column, you will find a small checkbox that you can use to specify the null-ability of that column. In other words, the index that is automatically created when you define a UNIQUE constraint will guarantee that no two rows in that table can have the same value for the columns participating in that index, with the ability to insert only one unique NULL value to these columns, if the column allows NULL.
Let us create a small table with two columns, ID and Name. The first two records will be inserted successfully, with no constraint preventing duplicate values of the Name column. Like Article. Last Updated : 09 Nov, Attention reader! Recommended Articles. What is NULL? What is dangling tuple problem? Article Contributed By :. Easy Normal Medium Hard Expert. Writing code in comment? You haven't really communicated much with your question.
Even i fill both fields, i still get the same error! Add a comment. Active Oldest Votes. Modather Seddik Modather Seddik 29 3 3 bronze badges. I dit it, but no chance : still the same error! Are you looking for an insert which will insert when data is not null in particular column? Valli Valli 1, 1 1 gold badge 8 8 silver badges 12 12 bronze badges. When the form is submitted, if optional field contains value, i insert it Ahmad Gozin Ahmad Gozin 23 3 3 bronze badges. Soviut This is not useful as an answer.
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