[1.7.x] Fixed queries that may return unexpected results on MySQL due to typecasting.

This is a security fix. Disclosure will follow shortly.

Backport of 75c0d4ea3ae48970f788c482ee0bd6b29a7f1307 from master

1 files changed, 10 insertions, 0 deletions

diff --git a/docs/topics/db/sql.txt b/docs/topics/db/sql.txt
index 9dcc98a3cb..72ded4cbdb 100644
--- a/docs/topics/db/sql.txt
+++ b/docs/topics/db/sql.txt
@@ -66,6 +66,16 @@ options that make it very powerful.
     database, but does nothing to enforce that. If the query does not
     return rows, a (possibly cryptic) error will result.
 
+.. warning::
+
+    If you are performing queries on MySQL, note that MySQL's silent type coercion
+    may cause unexpected results when mixing types. If you query on a string
+    type column, but with an integer value, MySQL will coerce the types of all values
+    in the table to an integer before performing the comparison. For example, if your
+    table contains the values ``'abc'``, ``'def'`` and you query for ``WHERE mycolumn=0``,
+    both rows will match. To prevent this, perform the correct typecasting
+    before using the value in a query.
+
 Mapping query fields to model fields
 ------------------------------------