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Constraints on lnvalid Data

By default, MySQL is forgiving of irwalid or improper data values and coerces them to valid values

for data entry. However, you can change the server SQL modę to select morę traditional treatment

of bad values such that the server rejects them and aborts the statement

in which they occur. See

Section 5.1.7, “Server SQL Modes”.

This section describes the default (forgiving) behavior of MySQL, as well as the strict SQL modę and how it differs.

If you are not using strict modę, then whenever you insert an “incorrect” value into a column, such as

a null into a not null column or a too-large numeric value into a numeric column, MySQL sets the

column to the “best possible value” instead of producing an error: The following rules describe in morę detail how this works: