IS NULL function in SQLite?
IS NULL function in SQLite?
Description. The SQLite ifnull function allows you to return an alternate value if expression1 is NULL. In other words, it will return the first non-null expression which is the same as using the coalesce function with 2 parameters.
How does SQLite handle NULL values?
Syntax. Following is the basic syntax of using NULL while creating a table. SQLite> CREATE TABLE COMPANY( ID INT PRIMARY KEY NOT NULL, NAME TEXT NOT NULL, AGE INT NOT NULL, ADDRESS CHAR(50), SALARY REAL ); Here, NOT NULL signifies that the column should always accept an explicit value of the given data type.
Is NVL same as Isnull?
ISNULL replaced the Oracle NVL function in the SQL server. When an expression in SQL server is NULL, the ISNULL function allows you to return an alternative value for the null. ISNULL checks whether the value or an expression is true or false.
How can I tell if SQLite database is empty Android?
How do you check whether the database is empty or not? SELECT COUNT(DISTINCT `TABLE_NAME`) AS anyAliasName FROM `INFORMATION_SCHEMA`. `COLUMNS` WHERE `table_schema` = ‘yourDatabaseName’; The above syntax returns 0 if the database has notable otherwise it returns the number of tables.
Should I use NULL or empty string?
So, NULL is better. An empty string is useful when the data comes from multiple resources. NULL is used when some fields are optional, and the data is unknown.
What is the difference between Isnull and Ifnull?
IFNULL is equivalent to ISNULL. IFNULL is equivalent to COALESCE except that IFNULL is called with only two arguments. ISNULL(a,b) is different from x IS NULL . The arguments can have any data type supported by Vertica.
How do you check if any column has NULL value in SQL?
How to Test for NULL Values?
- SELECT column_names. FROM table_name. WHERE column_name IS NULL;
- SELECT column_names. FROM table_name. WHERE column_name IS NOT NULL;
- Example. SELECT CustomerName, ContactName, Address. FROM Customers. WHERE Address IS NULL;
- Example. SELECT CustomerName, ContactName, Address. FROM Customers.
How do I query NULL values in SQL?
Which function is used to substitute for value if value is NULL?
We can replace NULL values with a specific value using the SQL Server ISNULL Function. The syntax for the SQL ISNULL function is as follow. The SQL Server ISNULL function returns the replacement value if the first parameter expression evaluates to NULL.
How can I tell if a database is empty?
SELECT COUNT(DISTINCT `TABLE_NAME`) AS anyAliasName FROM `INFORMATION_SCHEMA`. `COLUMNS` WHERE `table_schema` = ‘yourDatabaseName’; The above syntax returns 0 if the database has notable otherwise it returns the number of tables.
What is cursor in Android SQLite?
Cursors are what contain the result set of a query made against a database in Android. The Cursor class has an API that allows an app to read (in a type-safe manner) the columns that were returned from the query as well as iterate over the rows of the result set.
Is NULL the same as empty?
The main difference between null and empty is that the null is used to refer to nothing while empty is used to refer to a unique string with zero length.