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Agent skill

Comparing Database Schemas

by jeremylongshore in jeremylongshore/tons-of-skills-marketplace

Process use when you need to work with schema comparison. An agent skill from jeremylongshore/tons-of-skills-marketplace.

MITAuto-check passedDatabases

Install Comparing Database Schemas

skills CLI
$ npx skills add jeremylongshore/tons-of-skills-marketplace --skill comparing-database-schemas -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install jeremylongshore/tons-of-skills-marketplace comparing-database-schemas --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/jeremylongshore/tons-of-skills-marketplace.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/.curated/comparing-database-schemas .claude/skills/comparing-database-schemas && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
comparing-database-schemas
GitHub stars
2.8k
Token cost
~1.8k tokens
SKILL.md length
790 words
Files
5 (incl. scripts, references, assets)
Skills in repo
3,342
Repo updated
First seen
Licence
MIT

At a glance

Process use when you need to work with schema comparison. An agent skill from jeremylongshore/tons-of-skills-marketplace.

  • Works in 10 steps: Extract the full schema from both… → Compare tables present in each database → Compare columns for each shared table → …
  • You need to work with schema comparison
  • SKILL.md covers Overview, Prerequisites, Instructions and Output, plus 3 more sections
  • Runs Python scripts from its folder; calls pg_dump

What it does

Comparing Database Schemas is an agent skill from jeremylongshore/tons-of-skills-marketplace. Process use when you need to work with schema comparison. This skill provides database schema diff and sync with comprehensive guidance and automation. Trigger with phrases like "compare schemas", "diff databases", or "sync database schemas".

Its SKILL.md is about 1.8k tokens, which your agent loads only when the skill is triggered. The skill folder holds 7 other files, including scripts, reference files and assets (for example `assets/README.md`, `references/README.md` and `scripts/README.md`). Compatibility notes: Designed for Claude Code

It sits in Databases, covering Database schema design. It works with PostgreSQL and MySQL. The repository describes itself as: Model-agnostic agent-skills platform with a harness-free canonical layer, verified adapters, and the ccpi package manager. Explore at tonsofskills.com. The licence is MIT.

When your agent uses it

  • You need to work with schema comparison
  • With phrases like compare schemas
  • Sync database schemas

Example prompts

  • “compare schemas”
  • “diff databases”
  • “sync database schemas”
  • “/comparing-database-schemas”

Requirements

  • Python 3
  • Compatibility (from SKILL.md): Designed for Claude Code
  • Pre-approved tools (allowed-tools): Read, Write, Edit, Grep, Glob, Bash(psql:*), Bash(mysql:*), Bash(mongosh:*)

Workflow steps

10 steps, taken from the first numbered list in SKILL.md.

  1. Extract the full schema from both databases for comparison
  2. Compare tables present in each database
  3. Compare columns for each shared table
  4. Compare indexes
  5. Compare constraints (primary keys, foreign keys, unique, check)
  6. Compare functions, stored procedures, and triggers
  7. Compare enum types and custom types (PostgreSQL)
  8. Generate a structured diff report categorizing differences as
  9. Generate migration SQL to synchronize the target database to match the source
  10. Validate the generated migration by applying it to a copy of the target database and re-running the diff. The second diff should report…

What it can do on your machine

Read from SKILL.md and the folder at commit cfae287. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves these tools, so the agent can use them without asking each time:

    • Read
    • Write
    • Edit
    • Grep
    • Glob
    • Bash(psql:*)
    • Bash(mysql:*)
    • Bash(mongosh:*)

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Ships 2 files in scripts/ (Python), which the agent can run.

    Shell commands in SKILL.md call:

    • pg_dump

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    Links to these hosts (documentation or services it may open):

    • postgresql.org
    • github.com
    • skeema.io

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

  • Compatibility

    Designed for Claude Code

    From compatibility in the SKILL.md frontmatter.

Context cost

Comparing Database Schemas loads about 1.8k tokens when it runs, and up to ~1.8k if it reads all its reference files. Until then it costs about 67 tokens; SKILL.md has 790 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~67
When it runs · the whole SKILL.md, loaded when a task matches
~1.8k
With references · SKILL.md plus every file in references/, read only if the agent opens them
~1.8k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); the scripts in this folder are not scanned.

SKILL.md

The full file from jeremylongshore/tons-of-skills-marketplace at commit cfae287, republished under its MIT licence (© jeremylongshore). 790 words, ~1,810 tokens.

Download SKILL.mdSave it as .claude/skills/comparing-database-schemas/SKILL.md (or your agent's skills folder). This skill also uses 4 other files; get the full folder from GitHub.
name
comparing-database-schemas
description
Process use when you need to work with schema comparison. This skill provides database schema diff and sync with comprehensive guidance and automation. Trigger with phrases like "compare schemas", "diff databases", or "sync database schemas".
allowed-tools
Read, Write, Edit, Grep, Glob, Bash(psql:*), Bash(mysql:*), Bash(mongosh:*)
compatibility
Designed for Claude Code
version
1.27.0
author
Jeremy Longshore <jeremy@intentsolutions.io>
license
MIT
tags
database, comparing-database

Database Diff Tool

Overview

Compare database schemas between two environments (development vs. staging, staging vs.

Prerequisites

  • Connection credentials to both source and target databases
  • psql or mysql CLI configured to connect to both environments
  • Read access to information_schema and pg_catalog (PostgreSQL) or information_schema (MySQL)
  • Permission to run pg_dump --schema-only for full schema extraction
  • Understanding of which environment is the "source of truth" (typically the migration-managed environment)

Instructions

  1. Extract the full schema from both databases for comparison:

    • PostgreSQL: pg_dump --schema-only --no-owner --no-privileges -f schema_source.sql source_db and repeat for target_db
    • MySQL: mysqldump --no-data --routines --triggers source_db > schema_source.sql
    • Alternatively, query information_schema directly for programmatic comparison

  2. Compare tables present in each database:

    • SELECT table_name FROM information_schema.tables WHERE table_schema = 'public' AND table_catalog = 'source_db' EXCEPT SELECT table_name FROM information_schema.tables WHERE table_schema = 'public' AND table_catalog = 'target_db'
    • This reveals tables that exist in source but not in target (and vice versa)

  3. Compare columns for each shared table:

    • Query information_schema.columns from both databases for: column_name, data_type, character_maximum_length, is_nullable, column_default, ordinal_position
    • Flag differences in data type, nullability, default values, and column ordering
    • Detect added columns (in source, not target) and dropped columns (in target, not source)

  4. Compare indexes:

    • PostgreSQL: Query pg_indexes for indexname, indexdef on each database
    • MySQL: Query information_schema.STATISTICS for INDEX_NAME, COLUMN_NAME, NON_UNIQUE
    • Flag missing, extra, or differently-defined indexes

  5. Compare constraints (primary keys, foreign keys, unique, check):

    • Query information_schema.table_constraints and information_schema.key_column_usage
    • Detect missing foreign keys, changed constraint names, and altered check constraint expressions

  6. Compare functions, stored procedures, and triggers:

    • PostgreSQL: Query pg_proc for function signatures and pg_trigger for trigger definitions
    • MySQL: Query information_schema.ROUTINES and information_schema.TRIGGERS
    • Compare function bodies for logical differences

  7. Compare enum types and custom types (PostgreSQL):

    • Query pg_type and pg_enum for enum label differences
    • Detect added or removed enum values (note: PostgreSQL only supports adding enum values, not removing)

  8. Generate a structured diff report categorizing differences as:

    • Added: Objects in source not present in target (require CREATE statements)
    • Removed: Objects in target not present in source (require DROP statements, confirm intentional)
    • Modified: Objects differing between source and target (require ALTER statements)

  9. Generate migration SQL to synchronize the target database to match the source:

    • CREATE TABLE for new tables, ALTER TABLE ADD COLUMN for new columns
    • ALTER TABLE ALTER COLUMN for type changes, ALTER TABLE DROP COLUMN for removed columns
    • CREATE INDEX / DROP INDEX for index differences
    • Include transaction wrapping and rollback-safe operations

  10. Validate the generated migration by applying it to a copy of the target database and re-running the diff. The second diff should report zero differences, confirming the migration produces the expected state.

Output

  • Schema diff report listing all differences categorized by type (added, removed, modified)
  • Migration SQL script to synchronize target schema to match source
  • Rollback SQL script to reverse the migration if needed
  • Side-by-side comparison of differing object definitions
  • Drift detection summary highlighting changes not tracked in migration files
Show full SKILL.md (315 more words)Show less

Error Handling

ErrorCauseSolution
Connection refused to one databaseNetwork or credential issue on source or targetVerify connection strings; check firewall rules; confirm credentials work with direct psql or mysql connection
Permission denied on pg_catalog queriesUser lacks read access to system catalogsGrant pg_read_all_settings role; or use pg_dump --schema-only which requires fewer privileges
False positive differences from default value formattingPostgreSQL normalizes default expressions differently in different versionsNormalize default value strings before comparison; ignore whitespace differences; compare semantic equivalence
Enum type modification blockedPostgreSQL does not support removing enum values or reorderingCreate a new enum type, migrate the column, drop the old type; document this as a multi-step migration
Generated migration fails on targetTarget has data that violates new constraintsAdd data validation queries before constraint creation; backfill default values; handle edge cases in migration

Examples

Detecting schema drift between staging and production: After 3 months without auditing, the diff reveals: 2 columns added to production manually (not in migrations), 1 index missing from staging, and 3 functions with different implementations. A migration script is generated to bring staging in sync, and the manual production changes are backported into migration files.

Pre-deployment schema validation: Before deploying a release with 5 migration files, run the diff between the post-migration staging schema and the expected schema. The diff catches a migration that accidentally dropped a constraint that a later migration depends on. The migration ordering is fixed before production deployment.

Comparing PostgreSQL schemas across major version upgrade: Schema extracted from PostgreSQL 14 and compared against PostgreSQL 16 after migration. Diff reveals function signature changes for built-in function calls, updated default values for new parameters, and deprecated syntax in stored procedures. Migration script updates function definitions for the new version.

Resources

© jeremylongshore, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 4 other files (scripts, references, assets) in skills/.curated/comparing-database-schemas of jeremylongshore/tons-of-skills-marketplace.

  • SKILL.md
  • assets/README.md
  • references/README.md
  • scripts/README.md
  • scripts/generate_migration_script.py

Open the folder on GitHubat commit cfae287

Compare with similar skills

Comparing Database Schemas next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Comparing Database Schemas compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Comparing Database Schemas this skilljeremylongshore/tons-of-skills-marketplace2.8k—~1.8kAutomated safety check: PassMIT
Database DesignMoizIbnYousaf/ai-agent-skills1.1k1 repos~1.2kAutomated safety check: PassMIT
Golang Databaseunxed/f42432 repos~2.9kAutomated safety check: PassMIT
Database Expertcin12211/orca-q224—~2.8kAutomated safety check: PassMIT
DB Migrationhiromaily/go-crypto-wallet128—~652Automated safety check: PassMIT
Expert DatabaseReJeCtAll/ExpertTeam-Codex113—~692Automated safety check: PassMIT

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Works with

Categories

Questions about Comparing Database Schemas

What does Comparing Database Schemas do?

Process use when you need to work with schema comparison. An agent skill from jeremylongshore/tons-of-skills-marketplace. Comparing Database Schemas is an agent skill from jeremylongshore/tons-of-skills-marketplace. Process use when you need to work with schema comparison.

When should I use Comparing Database Schemas?

Comparing Database Schemas fits situations like: you need to work with schema comparison; with phrases like compare schemas; sync database schemas.

How do I install Comparing Database Schemas in Claude Code?

Run `npx skills add jeremylongshore/tons-of-skills-marketplace --skill comparing-database-schemas -a claude-code`. Or copy the skill folder (skills/.curated/comparing-database-schemas in jeremylongshore/tons-of-skills-marketplace) into .claude/skills/comparing-database-schemas in your project. Claude Code loads it when a task matches its description.

How do I install Comparing Database Schemas in Codex?

Run `npx skills add jeremylongshore/tons-of-skills-marketplace --skill comparing-database-schemas -a codex`. Or copy the skill folder (skills/.curated/comparing-database-schemas in jeremylongshore/tons-of-skills-marketplace) into .agents/skills/comparing-database-schemas in your project. Codex loads it when a task matches its description.

Can I use Comparing Database Schemas in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add jeremylongshore/tons-of-skills-marketplace --skill comparing-database-schemas -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/comparing-database-schemas, .gemini/skills/comparing-database-schemas, .github/skills/comparing-database-schemas and .opencode/skills/comparing-database-schemas in your project.

What does Comparing Database Schemas need to run?

Going by SKILL.md and its folder, Comparing Database Schemas needs Python for the scripts in its folder and the command-line tools its instructions call (pg_dump). Our summary lists: Python 3. Its frontmatter pre-approves these tools: Read, Write, Edit, Grep, Glob, Bash(psql:*), Bash(mysql:*), Bash(mongosh:*). Compatibility (from SKILL.md): Designed for Claude Code.

Does Comparing Database Schemas access the network?

SKILL.md names 3 domains. As links in the text: postgresql.org, github.com and skeema.io. This is read from the text; nothing was executed.

Is Comparing Database Schemas safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. The check reads SKILL.md only: the scripts in the folder are not scanned, so read them before running anything.

What licence does Comparing Database Schemas use?

Comparing Database Schemas is published under the MIT licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Comparing Database Schemas use?

About 1.8k tokens (SKILL.md is roughly 7.2k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 16 tokens, read only when the agent opens those files.

What are the alternatives to Comparing Database Schemas?

Skills that share tags, products or a category with Comparing Database Schemas: Database Design (MoizIbnYousaf/ai-agent-skills, 1.1k stars), Golang Database (unxed/f4, 243 stars), Database Expert (cin12211/orca-q, 224 stars) and DB Migration (hiromaily/go-crypto-wallet, 128 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Comparing Database Schemas?

jeremylongshore (a GitHub user) maintains it in jeremylongshore/tons-of-skills-marketplace, which has 2,827 GitHub stars. The repository holds 3,342 skills in this directory. The repository was last updated on October 10, 2026.

Source: jeremylongshore/tons-of-skills-marketplace on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.