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What not a likely primary key?
A field that is not unique and null can not be used as a primary key. Praimary key must satisfy the conditions of not null and unique.
Null means what in bank terms?
Null defines the value in a banking account as zero, no value. Zero or null are used to state the same idea on banking and investment documents.
What causes hypothesis to be rejected?
We have two types of hypothesis i.e., Null Hypothesis and Alternative Hypothesis. we take null hypothesis as the same statement given in the problem. Alternative hypothesis is the statement that is complementary to null hypothesis. When our calculated value is less than the tabulated value, we accept null hypothesis otherwise we reject null hypothesis.
Can you not reject null hypothesis?
you do not need to reject a null hypothesis. If you don not that means "we retain the null hypothesis." we retain the null hypothesis when the p-value is large but you have to compare the p-values with alpha levels of .01,.1, and .05 (most common alpha levels). If p-value is above alpha levels then we fail to reject the null hypothesis. retaining the null hypothesis means that we have evidence that something is going to occur (depending on the question)
Discuss the various reasons that lead to the occurrence of null values in relations?
If an instance (tuple) of a relation lacks having that attribute. i.e: a student that does not have a mobile phone or an office phones. The values for these attribute for that particular student will be null. It is important to note that a null value can mean either an unknown value, or a value that exists, but not yet available.
Can super key have null value?
No they can not
Have foreign keys null values?
Yes Foreign key can have null value.
Can a primary key have a blank or null value entered into its cell?
No. A Primary Key is the Unique identifier and cannot be null and cannot be duplicate.
Can you use more than one null value for unique key?
No.
Does primary key allows null value?
No. A primary key requires a value because it is the field that all other values in the row depend on.
What rule states that either each foreign key value must match a primary key value in another relation or the foreign key value must be null?
referential integrity constraint
Entity integrity constraint?
The entity integrity constraint states that no primary key value can be null. This is because the primary key value is used to identify individual tuples in a relation. Having null value for the primary key implies that we cannot identify some tuples. This also specifies that there may not be any duplicate entries in primary key column key row.
What is difference between null value and not null value?
Putting it very simply a null value is empty and a not null value contains something.
Explain two rules in relational model of database systems?
1) Entity Integrity: In a base relation, no attribute of a primary key can be null. 2) Referential Integrity: If foreign key exists in a relation, either foreign key value must match a candidate key value of some tuple in its home relation or foreign key value must be wholly null
Can a foreign key be null?
yes .a foreign key can have null values
What is the difference between an array shift and unsetting a variable in PHP?
By shifting the values in an array, you are moving a key's value to the previous key. The very first key's value is obliterated. By shifting all values in the array, all keys will have a value of NULL. Unsetting a variable is entirely different -- performing a variable unsetting causes the variable to have a value of NULL, as if it was never set.
Can unique key be null?
No unique can not be nulll....unique must have any unique value for unique identification.,...
