Can We Compare Two NULL Values In SQL?


The expression “NULL = NULL” evaluates to NULL, but is actually invalid in SQL; yet ORDER BY treats NULLs as equal (whatever they precede or follow “regular” values is left to DBMS vendor).

The expression “x IS NOT NULL” is not equal to “NOT(x IS NULL)”, as is the case in 2VL..

How do I check if an integer is null?

int cannot be null. If you are not assigning any value to int default value will be 0. If you want to check for null then make int as Integer in declaration. Then Integer object can be null.

How do I avoid NULL values in select query?

how to avoid null or ‘ ‘ value in a select query and replace that value as 0 in a select query not in the table? Use CASE to specifiy various conditions. Note that it has to use ‘0’ (with quotes) instead of 0, because the column ‘val’ is varchar (try removing the quotes and see what it does).

How do I stop null values in SQL?

A NOT NULL constraint in SQL is used to prevent inserting NULL values into the specified column, considering it as a not accepted value for that column. This means that you should provide a valid SQL NOT NULL value to that column in the INSERT or UPDATE statements, as the column will always contain data.

Can foreign key be null?

A foreign key containing null values cannot match the values of a parent key, since a parent key by definition can have no null values. However, a null foreign key value is always valid, regardless of the value of any of its non-null parts. … A table can have many foreign keys.

How do you compare null?

Use c == null , since you’re comparing references, not objects. The equals method (usually) expects an argument of type customer, and may be calling some methods on the object. If that object is null you will get the NullPointerException. Most likely Object c is null in this case.

IS NULL or == null?

There is in fact a difference in semantics between the two comparisons when you are comparing null with a type that has overloaded the == operator. foo is null will use direct reference comparison to determine the result, whereas foo == null will of course run the overloaded == operator if it exists.

How do you coalesce in SQL?

The SQL COALESCE function can be syntactically represented using the CASE expression. For example, as we know, the Coalesce function returns the first non-NULL values. SELECT COALESCE (expression1, expression2, expression3) FROM TABLENAME; The above Coalesce SQL statement can be rewritten using the CASE statement.


Let’s look at an example of how to use the IS NOT NULL condition in a SELECT statement in SQL Server. For example: SELECT * FROM employees WHERE last_name IS NOT NULL; This SQL Server IS NOT NULL example will return all records from the employees table where the last_name does not contain a null value.

Can we compare NULL values in SQL?

In SQL Server, NULL value indicates an unavailable or unassigned value. The value NULL does not equal zero (0), nor does it equal a space (‘ ‘). Because the NULL value cannot be equal or unequal to any value, you cannot perform any comparison on this value by using operators such as ‘=’ or ‘<>‘.

How do I compare two columns with null values in SQL?

2 Answers. Use <=> (null-safe equality operator) negated comparison which returns FALSE in case one of the operands is null but TRUE when both are null and both operands have equal non-null values.

How do you handle NULL value?

But enough bragging, here’s my list of practices when dealing with null values.Don’t Overcomplicate Things. … Use Objects Methods as Stream Predicates. … Never Pass Null as an Argument. … Validate Public API Arguments. … Return Empty Collections Instead of Null. … Optional Ain’t for Fields. … Use Exceptions Over Nulls. … Test Your Code.More items…•

Which one sorts rows in SQL?

The ORDER BY keyword is used to sort the result-set in ascending or descending order. The ORDER BY keyword sorts the records in ascending order by default. To sort the records in descending order, use the DESC keyword.

How do you check if a string is null?

To check if a string is null or empty in Java, use the == operator. Let’s say we have the following strings. String myStr1 = “Jack Sparrow”; String myStr2 = “”; Let us check both the strings now whether they are null or empty.

Can a unique key be null?

Unique fields in SQL Server are created using unique constraints or unique indexes, furthermore, each unique constraint uses a unique index. Regardless of using unique constraint or unique index, the field can accept null values, however the uniqueness will result in only accepting a single row with null value.

Is StringUtils equals null safe?

The compare() method in StringUtils class is a null-safe version of the compareTo() method of String class and handles null values by considering a null value less than a non-null value. Two null values are considered equal.

Is equal to null in Java?

equals(Object) : For any non-null reference value x , x. equals(null) should return false . The way to compare with null is to use x == null and x !=

What are null values in SQL?

A field with a NULL value is a field with no value. If a field in a table is optional, it is possible to insert a new record or update a record without adding a value to this field. Then, the field will be saved with a NULL value. Note: A NULL value is different from a zero value or a field that contains spaces.

Does equalsIgnoreCase handle null?

The equalsIgnoreCase() method compares two strings irrespective of the case (lower or upper) of the string. This method returns true if the argument is not null and it represents an equivalent String ignoring case, else false.

Can two NULL values be compared?

A comparison to NULL is never true or false. Since NULL can never be equal to any value, it can never be unequal, either.

How do you handle null values in SQL?

Functions and Operators for Handling NULL Values The COALESCE and ISNULL T-SQL functions are used to return the first non- null expression among the input arguments. Both are used to handle the NULL value in T-SQL. ISNULL takes two arguments and COALESCE takes more than two arguments as required.