Data compare and sync
Match tables of other names, map or leave out columns, pick the key that pairs rows, and filter what is compared with a WHERE condition. Show only the columns that differ.
Free for Windows · PostgreSQL · SQL Server · MySQL
Compare databases.
Deploy with confidence.
Parallax shows every difference in schema and data between two databases, writes the SQL to make one match the other, and checks the target before and after it runs.
Parallax · Release 2.4 vs production
Tested against every supported version, on every change
How it works
From difference to deployed, in four steps
- 1
Compare
Pick two databases, or one schema in each. Parallax lists every table, view, function, index and the rest that is new, missing or different, with both definitions side by side.
Parallax - 2
Deploy
Choose the differences to deploy and review the script. Parallax warns about statements that alter or recreate objects, then runs it, in one transaction where the database allows.
Parallax - 3
Sync the data
Compare the rows of matching tables, see which are new, missing or changed, and run a script that makes the target match, with foreign keys checked before it commits.
Parallax - 4
Promote through environments
Chain dev, staging and production in a pipeline. Compare every hop in one go, deploy a hop from the pipeline, and the next hop is compared again.
Parallax
Live demo
Click around a comparison
A release database against production. Pick an object to see both definitions, open its change script, then press Deploy.
Release 2.4 vs production
PostgreSQL#1DifferentXDevelopment
release / appYProduction prod / app↻4Different
+2Only in source
−1Only in target
Table
app.orders
Exists on both sides with different definitions. Deploying alters or recreates it in the target.
● Target (Y)
● Source (X)
CREATE TABLE app.orders (
CREATE TABLE app.orders (
id bigint GENERATED BY DEFAULT AS IDENTITY,
id bigint GENERATED BY DEFAULT AS IDENTITY,
customer_id bigint NOT NULL,
customer_id bigint NOT NULL,
status app.order_status NOT NULL DEFAULT 'new',
status app.order_status NOT NULL DEFAULT 'new',
ordered_at timestamptz NOT NULL,
ordered_at timestamptz NOT NULL,
shipped_at timestamptz,
shipped_at timestamptz,
total app.positive_amount,
total app.positive_amount,
− priority smallint NOT NULL DEFAULT 3,
+ priority smallint NOT NULL DEFAULT 5,
client_ip inet,
client_ip inet,
+ external_ref uuid,
CONSTRAINT orders_pkey PRIMARY KEY (id)
CONSTRAINT orders_pkey PRIMARY KEY (id)
);
);
Safe deployments
Production is not the place to find out
Writing the script is the easy part. Parallax checks the things that make a deployment fail halfway or quietly do the wrong thing, before any statement runs.
How deployments workNothing changed behind your back
Before it runs, Parallax compares the databases again. If someone changed them since, it shows what changed and offers to compare again first.
MySQL rows checked first
On MySQL, Parallax counts the rows that would make a change fail (duplicates under a new unique index, NULLs under NOT NULL) and stops before the first change.
All or nothing
On PostgreSQL and SQL Server the deployment runs in one transaction. If any statement fails, nothing changes.
MySQL, rehearsed too
MySQL can't roll back schema changes, so Parallax rehearses the deployment on a scratch copy of the target's schema before it touches the real one.
Compared again afterwards
When the deployment finishes, Parallax compares the two databases again to confirm the target now matches.
Every run kept
Every comparison and deployment is saved, with the SQL that ran, so you can see what changed and when.
Renames
A rename is not a drop and a create
Rename clients to customers and a comparison sees one table missing and another new. Deploy that, and the rows go with it. In Parallax, mark them as the same object and it renames instead.
Comparison
app.clientsOnly in target
app.customersOnly in source
app.clients → app.customersRenamed
Keys, indexes, checks and the foreign keys that point at it follow the new name.
Deployment script
DROP TABLE app.clients; CREATE TABLE app.customers ( id bigint NOT NULL, email varchar(320), … );
ALTER TABLE app.clients RENAME TO customers; ALTER INDEX app.clients_pkey RENAME TO customers_pkey;
48,211 rows lost
48,211 rows kept, history too
Pipelines
Every environment, one view
Chain your databases from dev to production and compare every hop in one go. Deploy a hop from the pipeline: it shows the comparison made after the deployment, and the next hop is compared again, since its source changed.
1devDevelopment
shop_dev / app2stagingStaging
shop_staging / app3prodProduction
shop_prod / appAnd the rest
Everything around the compare
ERDs
Draw an entity-relationship diagram of any database, arrange it, and export it as an image or to Lucidchart.
Snapshots
Save a copy of a database's schema, to look back at how it was.
History
Every comparison and deployment is kept, with the SQL each deployment ran, ready to copy.
Amazon RDS and managed hosts
Verified TLS with your provider's CA bundle. Accounts with fewer rights compare what they can see, and Parallax says which right to grant for the rest.
Local and private
Parallax runs on your machine and connects straight to your databases. Saved passwords are encrypted for your Windows account.
Is Parallax really free?+
Yes. Download it from the Microsoft Store and use every feature: schema and data compare, deployments, pipelines, ERDs and snapshots.
Which databases does it support?+
PostgreSQL (tested on 13, 16 and 17), SQL Server (2019 and 2022) and MySQL (8.0 and 8.4), including managed hosts like Amazon RDS. Both databases in a comparison use the same engine.
Does my data or schema leave my machine?+
No. Parallax runs on your computer and connects straight to your databases. Your projects and history are kept in a local file, and saved passwords are encrypted for your Windows account.
What happens if a deployment fails halfway?+
On PostgreSQL and SQL Server the whole deployment runs in one transaction, so if anything fails nothing changes. MySQL cannot roll back schema changes, so Parallax rehearses the deployment on a scratch copy of the schema and checks the rows first.
Can I review the SQL before it runs?+
Always. You pick the differences to deploy, read the whole script with its warnings, and can add your own SQL to run before and after it. You can also copy the script and run it yourself.
Does it work with an account that has limited rights?+
Yes. Parallax compares what the account can see and leaves out the rest on both sides, so nothing shows as a false difference. It tells you what was left out and which right to grant.
Which versions of Windows does it run on?+
Windows 10 and Windows 11, 64-bit.
See what changed. Ship it safely.
Free on the Microsoft Store for Windows 10 and 11.
