Add Connect To A Database In Safe Update Mode as a MySQL TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
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@@ -579,6 +579,7 @@ _1385 TILs and counting..._
 ### MySQL
 
 - [Change Existing Column To Not Null](mysql/change-existing-column-to-not-null.md)
+- [Connect To A Database In Safe Update Mode](mysql/connect-to-a-database-in-safe-update-mode.md)
 - [Default Username And Password For New Instance](mysql/default-username-and-password-for-new-instance.md)
 - [Display Output In A Vertical Format](mysql/display-output-in-a-vertical-format.md)
 - [Doing Date Math](mysql/doing-date-math.md)

mysql/connect-to-a-database-in-safe-update-mode.md

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+# Connect To A Database In Safe Update Mode
+
+The MySQL client has a _Safe-Updates Mode_ that you can use when connecting to
+a database. When this mode is active, the client will interrupt `update` and
+`delete` commands that don't specify a `where` clause that filters by a _key_
+value. That, or you need to explicitly `limit` the number of rows impacted by
+the query.
+
+To start a connection in this mode, you can use either the `--safe-updates`
+flag or the cheekier `--i-am-a-dummy` flag.
+
+```bash
+$ mysql --i-am-a-dummy -h ::1 -P 3309 -u root -D my-database
+```
+
+Then if you try to do an unrestricted `update` or `delete`, you'll see the
+following message:
+
+```sql
+mysql> update users set email = 'oops@email.com';
+ERROR 1175 (HY000): You are using safe update mode and you tried to update
+a table without a WHERE that uses a KEY column.
+```
+
+This can also be set within the connection like so:
+
+```sql
+mysql> set sql_safe_updates=1;
+```
+
+[source](https://dev.mysql.com/doc/refman/8.0/en/mysql-tips.html#safe-updates)