Add Transition A Branch From One Base To Another as a Git TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1249 TILs and counting..._
+_1251 TILs and counting..._
 
 ---
 
@@ -317,6 +317,7 @@ _1249 TILs and counting..._
 - [Stashing Only Unstaged Changes](git/stashing-only-unstaged-changes.md)
 - [Stashing Untracked Files](git/stashing-untracked-files.md)
 - [Switch To A Recent Branch With FZF](git/switch-to-a-recent-branch-with-fzf.md)
+- [Transition A Branch From One Base To Another](git/transition-a-branch-from-one-base-to-another.md)
 - [Turn Off The Output Pager For One Command](git/turn-off-the-output-pager-for-one-command.md)
 - [Two Kinds Of Dotted Range Notation](git/two-kinds-of-dotted-range-notation.md)
 - [Unstage Changes Wih Git Restore](git/unstage-changes-with-git-restore.md)
@@ -522,6 +523,7 @@ _1249 TILs and counting..._
 
 ### MySQL
 
+- [Change Existing Column To Not Null](mysql/change-existing-column-to-not-null.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)

git/transition-a-branch-from-one-base-to-another.md

@@ -0,0 +1,23 @@
+# Transition A Branch From One Base To Another
+
+Let's say I'm working in a git workflow where we have `main` as our production
+branch and `dev` as our development branch. I've opened a feature branch off of
+`main` and made a series of commits. It is at that point that I realize I
+should instead be branched off `dev`. I could open up a new branch off `dev`
+and then `cherry-pick` those commits. That is messier and more steps than
+necessary.
+
+Instead, I can transition the feature branch I'm already working from to a
+different base.
+
+The [`git-rebase`](https://git-scm.com/docs/git-rebase) command supports this
+with the `--onto` flag.
+
+```bash
+$ git rebase --onto dev main my-feature-branch
+```
+
+Specify the new base branch (`dev`), the current base (`main`), and then the
+name of the branch you are transitioning (`my-feature-branch`).
+
+[source](https://stackoverflow.com/a/10853956/535590)

mysql/change-existing-column-to-not-null.md

@@ -0,0 +1,27 @@
+# Change Existing Column To Not Null
+
+Let's say you have an existing nullable column. You want to update the schema
+to enforce a `not null` constraint on that column. You can do that with an
+[`alter table`](https://dev.mysql.com/doc/refman/8.0/en/alter-table.html) DDL
+statement. You can do this with the `modify` or `change` option.
+
+With `modify` you redeclare the column definition with the options that you
+want. You'll need to know and specify the existing data type of that column.
+
+```sql
+alter table books modify publication_year int not null;
+```
+
+It is possible, but clumsy to do this with the `change` option because you
+declare the column name twice. That's because `change` is typically used to
+rename a column.
+
+```sql
+alter table books change publication_year publication_year int not null;
+```
+
+If you're updating a column for a table that already contains data, make a plan
+to backfill any existing records that have `null` for that column. Every record
+will need a value in that column before the `modify` can be applied.
+
+[source](https://stackoverflow.com/a/6305252/535590)