Oracle SQL to SQL Server Converter

What Is the Oracle SQL to SQL Server Converter?

The Oracle SQL to SQL Server Converter is a free, browser-based tool that automatically translates Oracle SQL and PL/SQL syntax into equivalent Microsoft SQL Server T-SQL. Whether you are migrating a legacy Oracle database to Azure SQL, SQL Server 2019, or SQL Server 2022, this tool eliminates hours of tedious manual rewriting. Simply paste your Oracle SQL statement or script, click convert, and receive clean, ready-to-run T-SQL in seconds.

Database migrations between Oracle and SQL Server are notoriously complex. The two platforms share ANSI SQL as a common foundation, but each has built up decades of proprietary extensions, data types, functions, and procedural language features that are entirely incompatible with the other. This Oracle to T-SQL converter bridges that gap automatically, handling the most common — and most frustrating — syntax differences so you can focus on validating logic rather than hunting down function names.

Why Migrating Oracle SQL to SQL Server Is Harder Than It Looks

Many developers assume that because both databases speak SQL, porting queries is straightforward. In practice, even a moderately complex Oracle query can contain half a dozen constructs that SQL Server simply does not recognize. Consider the following common pain points:

• Data type mismatches: Oracle uses VARCHAR2, NUMBER, DATE, and CLOB, while SQL Server uses NVARCHAR, DECIMAL, DATETIME2, and NVARCHAR(MAX). A direct copy-paste will fail immediately.
• ROWNUM vs. TOP / ROW_NUMBER(): Oracle's ROWNUM pseudo-column is used everywhere for pagination and limiting result sets. SQL Server uses TOP for simple limits and ROW_NUMBER() OVER() for keyset pagination — completely different syntax.
• Sequences vs. IDENTITY: Oracle relies on standalone sequence objects combined with triggers to auto-increment primary keys. SQL Server uses the IDENTITY property directly on a column, or the newer SEQUENCE object introduced in SQL Server 2012.
• Outer join syntax: Oracle's legacy (+) outer join notation is not supported in T-SQL. SQL Server requires ANSI LEFT JOIN / RIGHT JOIN syntax.
• String functions: Oracle uses NVL(), DECODE(), SUBSTR(), and INSTR(). SQL Server equivalents are ISNULL() or COALESCE(), CASE WHEN, SUBSTRING(), and CHARINDEX().
• Date arithmetic: Adding days to a date in Oracle is as simple as sysdate + 7. In T-SQL you must use DATEADD(day, 7, GETDATE()).
• PL/SQL procedural blocks: Oracle stored procedures, functions, and anonymous blocks use PL/SQL syntax with DECLARE, BEGIN, EXCEPTION, and END. T-SQL uses a different block structure, different exception handling (TRY...CATCH), and different cursor syntax.

Manually resolving every one of these differences across thousands of lines of SQL is error-prone and slow. The Oracle SQL translator handles all of the above automatically.

How to Use the Oracle SQL to SQL Server Converter — Step by Step

1. Paste your Oracle SQL: Copy your Oracle SQL query, DDL statement, DML script, or PL/SQL block and paste it into the input panel on the left. The tool accepts single statements, multi-statement scripts, and complete stored procedure definitions.
2. Click Convert: Press the Convert button. The engine parses your Oracle SQL, identifies all platform-specific constructs, and produces the equivalent T-SQL in the output panel on the right.
3. Review the output: Read through the converted T-SQL carefully. The tool highlights any constructs that required non-trivial transformation so you can verify the logic is preserved.
4. Copy and test: Copy the T-SQL output and run it against your SQL Server instance. Use the tool's output as a strong starting point, then fine-tune for performance optimization, index hints, or business-specific logic.

Key Features of the Converter

Automatic Data Type Mapping

The converter applies a comprehensive Oracle to MSSQL data type mapping table, ensuring that every column definition is translated to the most appropriate SQL Server equivalent. Here is a summary of the most important mappings:

Function Translation

Beyond data types, the tool rewrites Oracle built-in functions to their SQL Server counterparts. NVL(expr, default) becomes ISNULL(expr, default). DECODE(col, val1, res1, val2, res2, default) is rewritten as a CASE WHEN expression. SUBSTR(str, start, len) becomes SUBSTRING(str, start, len). TO_DATE() and TO_CHAR() calls are converted to CONVERT() or FORMAT() with appropriate style codes.

Oracle ROWNUM to SQL Server Pagination

One of the trickiest conversions in any Oracle SQL to SQL Server migration is pagination. The tool correctly distinguishes between two common ROWNUM patterns. A simple WHERE ROWNUM <= 10 filter is converted to SELECT TOP 10. A more complex subquery-based pagination pattern — where an outer query filters on a ROWNUM alias — is converted to use ROW_NUMBER() OVER (ORDER BY ...) inside a CTE or subquery, which is the proper T-SQL approach.

Oracle Sequence to SQL Server IDENTITY

When the converter encounters Oracle sequence usage in a CREATE TABLE or INSERT statement, it rewrites the column definition to use SQL Server's IDENTITY(1,1) property. For cases where a standalone CREATE SEQUENCE statement is used independently (not tied to a single table), the tool generates the equivalent CREATE SEQUENCE syntax supported by SQL Server 2012 and later, preserving the start value and increment.

PL/SQL to T-SQL Block Conversion

The PL/SQL to T-SQL conversion handles anonymous blocks, stored procedures, and functions. EXCEPTION WHEN OTHERS THEN blocks are rewritten as BEGIN TRY ... END TRY BEGIN CATCH ... END CATCH structures. Oracle cursor syntax (OPEN, FETCH INTO, %NOTFOUND) is translated to T-SQL cursor declarations and @@FETCH_STATUS checks.

Real-World Use Cases

Database Migration Projects

Enterprise teams moving from Oracle on-premises to SQL Server on Azure or on-premises SQL Server use this tool to accelerate the SQL translation phase of their migration. Rather than manually converting hundreds of stored procedures one by one, developers can batch-process scripts and dramatically reduce migration timelines.

Cross-Platform Development

Some organizations run Oracle in production but use SQL Server for development or reporting. Developers can write queries in Oracle syntax — the environment they know best — and use this Oracle SQL translator to generate SQL Server-compatible versions for their reporting layer or ETL pipelines.

Learning and Training

Junior developers transitioning from Oracle to SQL Server use the converter as a learning aid. By comparing the Oracle input with the T-SQL output side by side, they quickly internalize the syntax differences and build fluency in T-SQL much faster than reading documentation alone.

Expert Tips for Getting the Best Results

• Convert one logical unit at a time: For large migration projects, convert individual stored procedures or views rather than dumping an entire schema into the tool at once. This makes it easier to review and test each unit independently.
• Always test date logic carefully: Oracle's DATE type stores both date and time, while SQL Server's DATE type stores only the date. The converter maps Oracle DATE to DATETIME2, but double-check any date comparison logic to ensure time components are handled as expected.
• Validate NULL handling: Oracle treats empty strings as NULL; SQL Server does not. Review any string comparison logic after conversion, especially in WHERE clauses and CASE expressions.
• Check implicit type conversions: Oracle is more permissive with implicit conversions between numbers and strings. After converting, add explicit CAST() or CONVERT() calls where SQL Server might raise a type mismatch error.
• Review TOP vs. ROWNUM semantics: ROWNUM is assigned before ORDER BY in Oracle, which can produce unexpected results. The converter generates correct T-SQL, but verify that your intended sort order is explicitly stated in the converted query.

Common Mistakes to Avoid When Migrating Oracle to MSSQL

Even with automated conversion, certain mistakes appear repeatedly in Oracle-to-SQL Server migrations. Avoid these pitfalls:

• Assuming that SYSDATE and GETDATE() return identical precision — they do not. Use SYSDATETIME() in SQL Server when microsecond precision matters.
• Forgetting that Oracle sequences are schema objects that can be shared across multiple tables. When converting to SQL Server IDENTITY, each table gets its own counter, which changes the behavior if multiple tables shared a single Oracle sequence.
• Overlooking Oracle's CONNECT BY hierarchical queries. These require a complete rewrite using SQL Server's recursive WITH ... AS (... UNION ALL ...)` CTE syntax, which the tool handles but which always warrants manual review.
• Ignoring Oracle DUAL table references. The converter removes FROM DUAL automatically since SQL Server allows SELECT without a FROM clause, but verify that no custom DUAL table exists in your schema.

Conclusion

Migrating from Oracle to SQL Server is one of the most common and most challenging database platform transitions in enterprise IT. The Oracle SQL to SQL Server Converter removes the most tedious part of that process — manually rewriting syntax, data types, and functions — so your team can focus on validating business logic, tuning performance, and delivering a successful migration. Use it as your first step in any Oracle-to-MSSQL migration workflow, and combine it with thorough testing to ensure your converted T-SQL behaves exactly as intended.