What does is mean in oracle?

Is in Oracle is a conditional statement used to determine whether a value meets a given condition. It is generally used together with other conditional statements (such as where, having, etc.) to filter and filter data.

Specifically, is can be used in the following situations:

1. Determine whether a value is null. In Oracle, null represents an unknown or inapplicable value. Therefore, we need to use is null or is not null statement to check if a certain value is null.

For example, suppose we have a table named employees that contains a column named salary. We can use the following statement to query how many employees have null salary:

SELECT COUNT(*) FROM employees WHERE salary IS NULL;

This will return the number of rows in the table with null salary.

2. Determine whether two values ​​are equal. When we need to compare two values ​​for equality, we usually use the equal sign (=) to perform the comparison. But in Oracle, if both values ​​are null, there is no way to tell whether they are equal using the equals sign. Therefore, we need to use the is statement to determine whether they are equal.

For example, let's say we have a table called customers that contains a column called phone_number. We can use the following statement to query which customers did not provide a phone number:

SELECT customer_name FROM customers WHERE phone_number IS NULL;

This will return a list containing the names of customers who did not provide a phone number.

3. Determine whether a value belongs to a certain set. When we need to check whether a value belongs to a set, we usually use the in operator. But in Oracle, if we need to check whether a value does not belong to a set, we need to use the is not in statement.

For example, suppose we have a table named orders, which contains a column named status. We can use the following statement to query all orders with a status other than 'pending' or 'processing':

SELECT * FROM orders WHERE status NOT IN ('pending', 'processing');

This will return a list containing all orders with a status other than 'pending' and 'processing'.

Summary:

In Oracle, is is a keyword used in conditional statements. It is mainly used to determine whether a value is null, whether two values ​​are equal, or whether Whether a value belongs to a set. Proficient in the use of the is statement can help us filter and filter data more easily, thereby processing data more efficiently.

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