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21 sie 2010 · 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. Solution SELECT pid FROM planets WHERE userid IS NULL; To test for NULL, use the IS NULL and IS NOT NULL operators. operator IS NULL tests whether a value is NULL.
Make sure your AUTO_INCREMENT is not out of range. In that case, set a new value for it with: ALTER TABLE table_name AUTO_INCREMENT=100 -- Change 100 to the desired number Explanation. AUTO_INCREMENT can contain a number that is bigger than the maximum value allowed by the
5.3.4.6 Working with NULL Values. The NULL value can be surprising until you get used to it. Conceptually, NULL means “a missing unknown value” and it is treated somewhat differently from other values. To test for NULL, use the IS NULL and IS. NOT NULL operators, as shown here:
31 lip 2024 · We can insert NULL values into the columns that allow them: INSERT INTO employees (name, salary) VALUES ('Alice', NULL); INSERT INTO employees (name, salary) VALUES (NULL, 50000.00); Querying NULL Values. To handle NULL values in queries we must use specific SQL functions and operators.
You can use a NULL value in the INSERT statement to specify that the data is missing. For example, the following statement inserts a row into the leads table. Because the phone number is missing, so a NULL value is used. INSERT INTO leads(first_name,last_name, source,email,phone)
26.2.7 How MySQL Partitioning Handles NULL. Partitioning in MySQL does nothing to disallow NULL as the value of a partitioning expression, whether it is a column value or the value of a user-supplied expression. Even though it is permitted to use NULL as the value of an expression that must otherwise yield an integer, it is important to keep in ...
If strict SQL mode is enabled, MySQL rejects the out-of-range value with an error, and the insert fails, in accordance with the SQL standard. If no restrictive modes are enabled, MySQL clips the value to the appropriate endpoint of the column data type range and stores the resulting value instead.
