[Git Basics]
# Created by Linus Torvalds in 2005
Git is a free and open-source Version Control System (VCS).

It allows you to:
• Track changes in your files over time
• Go back to any previous version if something breaks
• Collaborate with others without conflicts
• Create branches to test new ideas safely

[GitHub Basics]

GitHub is a web-based platform that hosts Git repositories in the cloud.

It is the most popular Git hosting service used by millions of developers and DBAs worldwide.

[root@git ~]# dnf install git -y
Last metadata expiration check: 3:39:21 ago on Mon 11 May 2026 02:42:47 PM.
Dependencies resolved.
========================================================================================
 Package                Architecture Version                  Repository           Size
========================================================================================
Installing:
 git                    x86_64       2.47.3-1.el9_6           ol9_appstream        65 k
Installing dependencies:
 git-core               x86_64       2.47.3-1.el9_6           ol9_appstream       4.7 M
 git-core-doc           noarch       2.47.3-1.el9_6           ol9_appstream       4.1 M
 perl-Error             noarch       1:0.17029-7.el9          ol9_appstream        57 k
 perl-Git               noarch       2.47.3-1.el9_6           ol9_appstream        42 k
 perl-TermReadKey       x86_64       2.38-11.el9              ol9_appstream        42 k
 perl-lib               x86_64       0.65-481.1.el9_6         ol9_appstream        13 k

Transaction Summary
========================================================================================
Install  7 Packages

Total download size: 9.0 M
Installed size: 40 M
Downloading Packages:
(1/7): git-core-2.47.3-1.el9_6.x86_64.rpm               6.0 MB/s | 4.7 MB     00:00
(2/7): perl-Error-0.17029-7.el9.noarch.rpm              223 kB/s |  57 kB     00:00
(3/7): perl-Git-2.47.3-1.el9_6.noarch.rpm               172 kB/s |  42 kB     00:00
(4/7): perl-TermReadKey-2.38-11.el9.x86_64.rpm          1.1 MB/s |  42 kB     00:00
(5/7): perl-lib-0.65-481.1.el9_6.x86_64.rpm             483 kB/s |  13 kB     00:00
(6/7): git-core-doc-2.47.3-1.el9_6.noarch.rpm           1.7 MB/s | 4.1 MB     00:02
(7/7): git-2.47.3-1.el9_6.x86_64.rpm                     20 kB/s |  65 kB     00:03
----------------------------------------------------------------------------------------
Total                                                   2.8 MB/s | 9.0 MB     00:03
Oracle Linux 9 Application Stream Packages (x86_64)     4.3 MB/s | 6.2 kB     00:00
Importing GPG key 0x8D8B756F:
 Userid     : "Oracle Linux (release key 1) <secalert_us@oracle.com>"
 Fingerprint: 3E6D 826D 3FBA B389 C2F3 8E34 BC4D 06A0 8D8B 756F
 From       : /etc/pki/rpm-gpg/RPM-GPG-KEY-oracle
Key imported successfully
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Preparing        :                                                                1/1
  Installing       : git-core-2.47.3-1.el9_6.x86_64                                 1/7
  Installing       : git-core-doc-2.47.3-1.el9_6.noarch                             2/7
  Installing       : perl-lib-0.65-481.1.el9_6.x86_64                               3/7
  Installing       : perl-TermReadKey-2.38-11.el9.x86_64                            4/7
  Installing       : perl-Error-1:0.17029-7.el9.noarch                              5/7
  Installing       : perl-Git-2.47.3-1.el9_6.noarch                                 6/7
  Installing       : git-2.47.3-1.el9_6.x86_64                                      7/7
  Running scriptlet: git-2.47.3-1.el9_6.x86_64                                      7/7
  Verifying        : git-2.47.3-1.el9_6.x86_64                                      1/7
  Verifying        : git-core-2.47.3-1.el9_6.x86_64                                 2/7
  Verifying        : git-core-doc-2.47.3-1.el9_6.noarch                             3/7
  Verifying        : perl-Error-1:0.17029-7.el9.noarch                              4/7
  Verifying        : perl-Git-2.47.3-1.el9_6.noarch                                 5/7
  Verifying        : perl-TermReadKey-2.38-11.el9.x86_64                            6/7
  Verifying        : perl-lib-0.65-481.1.el9_6.x86_64                               7/7

Installed:
  git-2.47.3-1.el9_6.x86_64                  git-core-2.47.3-1.el9_6.x86_64
  git-core-doc-2.47.3-1.el9_6.noarch         perl-Error-1:0.17029-7.el9.noarch
  perl-Git-2.47.3-1.el9_6.noarch             perl-TermReadKey-2.38-11.el9.x86_64
  perl-lib-0.65-481.1.el9_6.x86_64

Complete!
[root@git ~]#

[root@git ~]# git --version
git version 2.47.3
[root@git ~]#

[git@git ~]$ git config --global user.name "Rajasekhar"
[git@git ~]$ git config --global user.email "br8dba@gmail.com"
[git@git ~]$ git config --list
user.name=Rajasekhar
user.email=br8dba@gmail.com
core.repositoryformatversion=0
core.filemode=true
core.bare=false
core.logallrefupdates=true
[git@git ~]$

[root@git ~]# groupadd git
[root@git ~]# useradd -g git -m -s /bin/bash git
[root@git ~]# passwd git
Changing password for user git.
New password:
Retype new password:
passwd: all authentication tokens updated successfully.
[root@git ~]#

[root@git ~]# su - git
[git@git ~]$ mkdir -p /home/git/repos
[git@git ~]$ cd /home/git/repos
[git@git repos]$

[git@git repos]$ git init
hint: Using 'master' as the name for the initial branch. This default branch name
hint: is subject to change. To configure the initial branch name to use in all
hint: of your new repositories, which will suppress this warning, call:
hint:
hint:   git config --global init.defaultBranch <name>
hint:
hint: Names commonly chosen instead of 'master' are 'main', 'trunk' and
hint: 'development'. The just-created branch can be renamed via this command:
hint:
hint:   git branch -m <name>
Initialized empty Git repository in /home/git/repos/.git/
[git@git repos]$

[git@git repos]$ pwd
/home/git/repos
[git@git repos]$ vi create_table.sql
[git@git repos]$ cat create_table.sql
CREATE TABLE emp (
    name        VARCHAR2(100),
    designation VARCHAR2(100),
    project     VARCHAR2(100),
    company     VARCHAR2(100)
);
[git@git repos]$

[git@git repos]$ git status
On branch master

No commits yet

Untracked files:
  (use "git add <file>..." to include in what will be committed)
        create_table.sql

nothing added to commit but untracked files present (use "git add" to track)
[git@git repos]$

-- Git sees the file but is NOT tracking it yet.

[git@git repos]$ git add create_table.sql
[git@git repos]$

[git@git repos]$ git status
On branch master

No commits yet

Changes to be committed:
  (use "git rm --cached <file>..." to unstage)
        new file:   create_table.sql

[git@git repos]$

-- To add all files at once:
git add .

[git@git repos]$ git commit -m "Initial emp table"
[master (root-commit) 03feab3] Initial emp table
 1 file changed, 6 insertions(+)
 create mode 100644 create_table.sql
[git@git repos]$

[git@git repos]$ vi create_table.sql
[git@git repos]$ cat create_table.sql
CREATE TABLE emp (
    name        VARCHAR2(50),
    designation VARCHAR2(50),
    project     VARCHAR2(50),
    company     VARCHAR2(50)
);
[git@git repos]$

[git@git repos]$ git diff create_table.sql
diff --git a/create_table.sql b/create_table.sql
index ef15ed0..62f7356 100644
--- a/create_table.sql
+++ b/create_table.sql
@@ -1,6 +1,6 @@
 CREATE TABLE emp (
-    name        VARCHAR2(100),
-    designation VARCHAR2(100),
-    project     VARCHAR2(100),
-    company     VARCHAR2(100)
+    name        VARCHAR2(50),
+    designation VARCHAR2(50),
+    project     VARCHAR2(50),
+    company     VARCHAR2(50)
 );
[git@git repos]$

-- Red  (-) = removed lines
-- Green(+) = added lines

[git@git repos]$ git add create_table.sql
[git@git repos]$ git commit -m "Changed VARCHAR VALUES"
[master 0f8e7e6] Changed VARCHAR VALUES
 1 file changed, 4 insertions(+), 4 deletions(-)
[git@git repos]$

-- Git now internally stores Version 1 and Version 2.

[git@git repos]$ git log --oneline
0f8e7e6 (HEAD -> master) Changed VARCHAR VALUES
03feab3 Initial emp table
[git@git repos]$

[git@git repos]$ vi .gitignore
[git@git repos]$ cat .gitignore
# Ignore log files
*.log
*.log.*

# Ignore temp files
*.tmp
*.bak

# Ignore Oracle wallet / credential files
*.ora
wallet/
*.p12

# Ignore OS files
.DS_Store
Thumbs.db

[git@git repos]$ git add .gitignore
[git@git repos]$ git commit -m "Added .gitignore"
[master a1b2c3d] Added .gitignore
 1 file changed, 10 insertions(+)
 create mode 100644 .gitignore
[git@git repos]$

-- Verify ignored files are not tracked:
[git@git repos]$ git status
On branch master
nothing to commit, working tree clean
[git@git repos]$

ghp_KVxvib0FhfTp5NK3xxxBhE8E4h9BY4Uxxx

[git@git repos]$ git remote add origin https://github.com/ramudala/repo.git
[git@git repos]$

[git@git repos]$ git remote -v
origin  https://github.com/ramudala/repo.git (fetch)
origin  https://github.com/ramudala/repo.git (push)
[git@git repos]$

[git@git repos]$ git branch
* master
[git@git repos]$

[git@git repos]$ git branch -M main
[git@git repos]$ git branch
* main
[git@git repos]$

[git@git repos]$ git push -u origin main
Username for 'https://github.com': ramudala
Password for 'https://ramudala@github.com': [enter PAT token]
Enumerating objects: 6, done.
Counting objects: 100% (6/6), done.
Compressing objects: 100% (4/4), done.
Writing objects: 100% (6/6), 556 bytes | 185.00 KiB/s, done.
Total 6 (delta 1), reused 0 (delta 0), pack-reused 0 (from 0)
remote: Resolving deltas: 100% (1/1), done.
To https://github.com/ramudala/repo.git
 * [new branch]      main -> main
branch 'main' set up to track 'origin/main'.
[git@git repos]$

-- Step 1: Edit your SQL / script file
vi create_table.sql

-- Step 2: Check what changed
git status
git diff

-- Step 3: Stage all changes
git add .

-- Step 4: Commit with a meaningful message
git commit -m "Added index on emp.name"

-- Step 5: Push to GitHub
git push

[git@git repos]$ git pull
remote: Enumerating objects: 4, done.
remote: Counting objects: 100% (4/4), done.
remote: Compressing objects: 100% (2/2), done.
remote: Total 3 (delta 0), reused 0 (delta 0), pack-reused 0 (from 0)
Unpacking objects: 100% (3/3), 974 bytes | 974.00 KiB/s, done.
From https://github.com/ramudala/repo
   0f8e7e6..2b24839  main       -> origin/main
Updating 0f8e7e6..2b24839
Fast-forward
 create_table_emp1.sql | 3 +++
 1 file changed, 3 insertions(+)
 create mode 100644 create_table_emp1.sql
[git@git repos]$

[git@git repos]$ ls -ltr
total 8
-rw-r--r--. 1 git git 141 May 11 19:00 create_table.sql
-rw-r--r--. 1 git git  39 May 11 20:42 create_table_emp1.sql
[git@git repos]$

[git@git ~]$ cd repos/
[git@git repos]$ pwd
/home/git/repos

-- Create dev branch
[git@git repos]$ git checkout -b dev
Switched to a new branch 'dev'
[git@git repos]$

-- Create uat branch
[git@git repos]$ git checkout -b uat
Switched to a new branch 'uat'
[git@git repos]$

[git@git repos]$ git branch
  dev
  main
* uat
[git@git repos]$

-- * uat  →  currently checked out branch

-- Alternative modern syntax (Git 2.23+):
[git@git repos]$ git switch -c dev
fatal: a branch named 'dev' already exists
[git@git repos]$

-- Classic syntax
[git@git repos]$ git checkout main
Switched to branch 'main'
Your branch is up to date with 'origin/main'.
[git@git repos]$ git branch
  dev
* main
  uat
[git@git repos]$

-- Modern syntax (Git 2.23+)
[git@git repos]$ git switch dev
Switched to branch 'dev'
[git@git repos]$ git branch
* dev
  main
  uat
[git@git repos]$

-- Step 1: Make changes in dev branch
[git@git repos]$ git branch
* dev
  main
  uat
[git@git repos]$ echo "new code" >> test.sql
[git@git repos]$ git add test.sql
[git@git repos]$ git commit -m "Added new changes"
[dev 412d5c8] Added new changes
 1 file changed, 1 insertion(+)
 create mode 100644 test.sql
[git@git repos]$

-- Step 2: Switch back to main
[git@git repos]$ git checkout main
Switched to branch 'main'
Your branch is up to date with 'origin/main'.

-- Step 3: Merge dev into main
[git@git repos]$ git merge dev
Updating 2b24839..412d5c8
Fast-forward
 test.sql | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 test.sql
[git@git repos]$

-- DEV changes successfully merged into MAIN.

-- Push merged main to GitHub
[git@git repos]$ git push origin main
Username for 'https://github.com': ramudala
Password for 'https://ramudala@github.com':
Enumerating objects: 4, done.
Counting objects: 100% (4/4), done.
Compressing objects: 100% (2/2), done.
Writing objects: 100% (3/3), 279 bytes | 139.00 KiB/s, done.
Total 3 (delta 1), reused 0 (delta 0), pack-reused 0 (from 0)
remote: Resolving deltas: 100% (1/1), completed with 1 local object.
To https://github.com/ramudala/repo.git
   2b24839..412d5c8  main -> main
[git@git repos]$

-- Push dev branch to GitHub (make it visible in GitHub UI)
[git@git repos]$ git push -u origin dev
Username for 'https://github.com': ramudala
Password for 'https://ramudala@github.com':
Total 0 (delta 0), reused 0 (delta 0), pack-reused 0 (from 0)
remote:
remote: Create a pull request for 'dev' on GitHub by visiting:
remote:      https://github.com/ramudala/repo/pull/new/dev
remote:
To https://github.com/ramudala/repo.git
 * [new branch]      dev -> dev
branch 'dev' set up to track 'origin/dev'.
[git@git repos]$

[git@git repos]$ git branch
* dev
  main
  uat

-- Switch to main first (cannot delete the active branch)
[git@git repos]$ git switch main
M       create_table.sql
Switched to branch 'main'
Your branch is up to date with 'origin/main'.

-- Force delete local branch
[git@git repos]$ git branch -D dev
Deleted branch dev (was 412d5c8).
[git@git repos]$

-- Delete remote branch from GitHub
[git@git repos]$ git push origin --delete dev
Username for 'https://github.com': ramudala
Password for 'https://ramudala@github.com':
To https://github.com/ramudala/repo.git
 - [deleted]         dev
[git@git repos]$

-- Verify local branches
[git@git repos]$ git branch
* main
  uat
[git@git repos]$

-- Verify remote branches
[git@git repos]$ git branch -r
  origin/main
[git@git repos]$

-- View commit history for specific file
[git@git repos]$ git log --oneline create_table.sql
0f8e7e6 Changed VARCHAR VALUES
03feab3 Initial emp table
[git@git repos]$

-- Current file has VARCHAR2(50)
[git@git repos]$ cat create_table.sql
CREATE TABLE emp (
    name        VARCHAR2(50),
    designation VARCHAR2(50),
    project     VARCHAR2(50),
    company     VARCHAR2(50)
);
[git@git repos]$

-- Restore to original version (commit 03feab3 = VARCHAR2(100))
[git@git repos]$ git checkout 03feab3 create_table.sql
Updated 1 path from e30c8a7
[git@git repos]$

-- Verify restored file now has VARCHAR2(100)
[git@git repos]$ cat create_table.sql
CREATE TABLE emp (
    name        VARCHAR2(100),
    designation VARCHAR2(100),
    project     VARCHAR2(100),
    company     VARCHAR2(100)
);
[git@git repos]$

[oracle@git ~]$ id
uid=1001(oracle) gid=1001(oinstall) groups=1001(oinstall),1002(dba)
[oracle@git ~]$

[oracle@git ~]$ git clone https://github.com/ramudala/repo.git
Cloning into 'repo'...
remote: Enumerating objects: 12, done.
remote: Counting objects: 100% (12/12), done.
remote: Compressing objects: 100% (6/6), done.
remote: Total 12 (delta 2), reused 10 (delta 2), pack-reused 0 (from 0)
Receiving objects: 100% (12/12), done.
Resolving deltas: 100% (2/2), done.
[oracle@git ~]$

[oracle@git ~]$ ls -ltr
total 0
drwxr-xr-x. 3 oracle oinstall 87 May 12 15:00 repo
[oracle@git ~]$

[oracle@git ~]$ cd repo/
[oracle@git repo]$ ls -ltr
total 12
-rw-r--r--. 1 oracle oinstall   9 May 12 15:00 test.sql
-rw-r--r--. 1 oracle oinstall 141 May 12 15:00 create_table.sql
-rw-r--r--. 1 oracle oinstall  39 May 12 15:00 create_table_emp1.sql
[oracle@git repo]$