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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.
Summary: in this tutorial, you will learn how to work with MySQL NULL values. In addition, you’ll learn some useful functions to deal with the NULL values effectively. Introduction to MySQL NULL values. In MySQL, a NULL value means unknown. A NULL value is different from zero (0) or an empty string ''. A NULL value is not equal to anything ...
The IS NOT NULL operator is used to test for non-empty values (NOT NULL values). The following SQL lists all customers with a value in the "Address" field:
With strict SQL mode enabled, an out of range error occurs: mysql> SET sql_mode = 'TRADITIONAL'; mysql> INSERT INTO t1 (i1, i2) VALUES(256, 256); ERROR 1264 (22003): Out of range value for column 'i1' at row 1 mysql> SELECT * FROM t1; Empty set (0.00 sec) With strict SQL mode not enabled, clipping with warnings occurs:
The SQL Server ISNULL() function lets you return an alternative value when an expression is NULL: SELECT ProductName, UnitPrice * (UnitsInStock + ISNULL(UnitsOnOrder, 0)) FROM Products;
