AI SQL Assistant

SQL Dialect Comparisons

SQL is standardized, but each database system implements its own extensions and variations. This section helps you understand the differences and migrate between database systems.

Dialect Differences

Side-by-side comparison of SQL syntax across popular databases for common operations.

Migration Guides

Step-by-step guides for migrating from one database to another.

Feature Matrix

Comprehensive feature comparison across database systems including data types, SQL compliance, transactions, performance features, and cloud capabilities.

DML & DDL Differences

Detailed comparison of Data Manipulation Language (DML) and Data Definition Language (DDL) syntax across major SQL databases.

Interactive Comparison

📊 SQL Dialect Comparison

Compare SQL syntax across different database systems

PostgreSQL

-- Window function with ROWS frame
SELECT
  customer_id,
  order_date,
  amount,
  SUM(amount) OVER (
    PARTITION BY customer_id
    ORDER BY order_date
    ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
  ) as running_total
FROM orders;

Notes:

Full support for all window frame types. Most feature-complete implementation.

MySQL

-- Window function (MySQL 8.0+)
SELECT
  customer_id,
  order_date,
  amount,
  SUM(amount) OVER (
    PARTITION BY customer_id
    ORDER BY order_date
    ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
  ) as running_total
FROM orders;

Notes:

Window functions added in MySQL 8.0. Earlier versions not supported.

SQL Server

-- Window function with ROWS frame
SELECT
  customer_id,
  order_date,
  amount,
  SUM(amount) OVER (
    PARTITION BY customer_id
    ORDER BY order_date
    ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
  ) as running_total
FROM orders;

Notes:

Supports ROWS and RANGE frames. Highly optimized for analytical queries.

Common Differences by Topic

String Concatenation

Database	Syntax	Example
PostgreSQL	`\|\|` operator	`'Hello' \|\| ' ' \|\| 'World'`
MySQL	`CONCAT()` function	`CONCAT('Hello', ' ', 'World')`
SQL Server	`+` operator	`'Hello' + ' ' + 'World'`
Oracle	`\|\|` operator	`'Hello' \|\| ' ' \|\| 'World'`
SQLite	`\|\|` operator	`'Hello' \|\| ' ' \|\| 'World'`

Auto-Increment

Database	Syntax
PostgreSQL	`SERIAL` or `IDENTITY`
MySQL	`AUTO_INCREMENT`
SQL Server	`IDENTITY(1,1)`
Oracle	`SEQUENCE` and trigger
SQLite	`AUTOINCREMENT`

LIMIT / TOP

Database	Syntax
PostgreSQL	`LIMIT n OFFSET m`
MySQL	`LIMIT n OFFSET m`
SQL Server	`TOP n` or `OFFSET m ROWS FETCH NEXT n ROWS ONLY`
Oracle	`FETCH FIRST n ROWS ONLY` or `ROWNUM <= n`
SQLite	`LIMIT n OFFSET m`

Date Functions

Operation	PostgreSQL	MySQL	SQL Server
Current Date	`CURRENT_DATE`	`CURDATE()`	`GETDATE()`
Current Timestamp	`NOW()`	`NOW()`	`GETDATE()`
Date Add	`date + INTERVAL '1 day'`	`DATE_ADD(date, INTERVAL 1 DAY)`	`DATEADD(day, 1, date)`
Date Diff	`date1 - date2`	`DATEDIFF(date1, date2)`	`DATEDIFF(day, date1, date2)`
Extract Year	`EXTRACT(YEAR FROM date)`	`YEAR(date)`	`YEAR(date)`

String Functions

Operation	PostgreSQL	MySQL	SQL Server
Length	`LENGTH(str)` or `CHAR_LENGTH(str)`	`LENGTH(str)`	`LEN(str)`
Substring	`SUBSTRING(str, start, length)`	`SUBSTRING(str, start, length)`	`SUBSTRING(str, start, length)`
Upper Case	`UPPER(str)`	`UPPER(str)`	`UPPER(str)`
Lower Case	`LOWER(str)`	`LOWER(str)`	`LOWER(str)`
Trim	`TRIM(str)`	`TRIM(str)`	`TRIM(str)`

Popular Migration Paths

MySQL → PostgreSQL

PostgreSQL offers more advanced features and better standards compliance. Common reasons to migrate:

Better support for complex queries
Advanced data types (arrays, JSON, etc.)
Stronger ACID guarantees
More flexible licensing

View Migration Guide →

Oracle → PostgreSQL

Cost reduction is often a primary driver:

Open source and free
Similar feature set for most use cases
Strong community support
Active development

View Migration Guide →

SQL Server → PostgreSQL

Common in cloud migrations:

Lower licensing costs
Better Linux support
Cross-platform compatibility
Modern features

View Migration Guide →

Tools for Comparison

AI-Powered Translation

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See Also