How do I find NULL records in MySQL?

How do I find NULL records in MySQL?

To search for column values that are NULL , you cannot use an expr = NULL test. The following statement returns no rows, because expr = NULL is never true for any expression: mysql> SELECT * FROM my_table WHERE phone = NULL; To look for NULL values, you must use the IS NULL test.

How do you check if any column has null value in SQL?

How to Test for NULL Values?

1. SELECT column_names. FROM table_name. WHERE column_name IS NULL;
2. SELECT column_names. FROM table_name. WHERE column_name IS NOT NULL;
3. Example. SELECT CustomerName, ContactName, Address. FROM Customers. WHERE Address IS NULL;
4. Example. SELECT CustomerName, ContactName, Address. FROM Customers.

What is fulltext index in MySQL?

Full-text indexes are created on text-based columns ( CHAR , VARCHAR , or TEXT columns) to speed up queries and DML operations on data contained within those columns. A full-text index is defined as part of a CREATE TABLE statement or added to an existing table using ALTER TABLE or CREATE INDEX .

Why does MySQL index columns that are null?

Building the index can take a while on large tables even if the column is empty (all nulls). Reference. Allowing a column to be null will add a byte to the storage requirements of the column.

Is it possible to index a text column in MySQL?

You can’t have a UNIQUE index on a text column in MySQL. If you want to index on a TEXT or a BLOB field, you must specify a fixed length to do that.

Why are there only two null values in MySQL?

The query returns only two rows because the rows whose email column is NULL are grouped into one. When you use a UNIQUE constraint or UNIQUE index on a column, you can insert multiple NULL values into that column. It is perfectly fine because in this case, MySQL considers NULL values are distinct.

How to set an email to null in MySQL?

Because the phone number is missing, so a NULL value is used. Because the default value of the email column is NULL, you can omit the email in the INSERT statement as follows: To set the value of a column to NULL, you use the assignment operator ( = ).