Here are the top 25 most common and critical SQL Server errors encountered by DBAs and developers, categorized by domain, along with their causes, fixes, and example scenarios.
Section 1: Data & Integrity Errors
#
Error Code
Error Message
Cause
Fix/Solution
Example Scenario
1
2627
Violation of PRIMARY KEY constraint. Cannot insert duplicate key.
Trying to insert or update a row with a key value that already exists in the table.
Ensure the key value is unique, or check application logic for accidental duplicate inserts.
Two users submit the same form simultaneously, creating a duplicate customer ID.
2
547
The INSERT or UPDATE statement conflicted with the FOREIGN KEY constraint.
Attempting to insert a row with a Foreign Key value that does not exist in the parent table.
Insert the corresponding parent row first, or update the Foreign Key value to match an existing parent record.
Inserting an Order with a CustomerID that doesn’t exist in the Customers table.
3
515
Cannot insert the value NULL into column ‘X’; column does not allow nulls.
Trying to insert data into a column that is defined as NOT NULL without providing a value.
Provide a value for the column, or define a DEFAULT constraint for it.
Running an INSERT statement that omits a required field, like OrderDate.
4
8152
String or binary data would be truncated.
Trying to insert a string value that is longer than the column’s defined length (e.g., trying to put 60 characters into a VARCHAR(50) column).
Increase the column size in the table definition, or truncate/shorten the input data before insertion.
Inserting a long descriptive product name into a ProductName column limited to 100 characters.
5
208
Invalid object name ‘X’.
The table, view, or stored procedure name used in the query does not exist in the current database or schema.
Check for typos in the name, ensure the schema is correct (e.g., dbo.TableName), and verify the object exists.
Mistyping Customers as Customerz in a SELECT statement.
Section 2: Transaction & Locking Errors
#
Error Code
Error Message
Cause
Fix/Solution
Example Scenario
6
1205
Deadlock victim. Transaction was aborted.
Two concurrent transactions are mutually blocking each other, and SQL Server chose your transaction to terminate.
Analyze the Deadlock Graph (Extended Events) to find the cause. Modify the application to access resources in the same order.
Transaction A locks Table X, then requests a lock on Table Y. Transaction B locks Table Y, then requests a lock on Table X.
7
3902
The COMMIT TRANSACTION request has no corresponding BEGIN TRANSACTION.
Trying to commit a transaction when no active BEGIN TRANSACTION has been issued.
Ensure every COMMIT or ROLLBACK is preceded by a BEGIN TRANSACTION within the batch.
A stored procedure calls a COMMIT but the prior BEGIN TRAN was conditional and not executed.
8
50000
A custom error (often related to RAISERROR or THROW).
An error was intentionally raised by T-SQL code within a Stored Procedure, Function, or Trigger.
Review the source code of the stored procedure/trigger to understand the business logic that triggered the error.
A trigger prevents a sales order from being deleted if its status is ‘Invoiced’ and raises a custom error.
9
3621
The statement has been terminated.
The T-SQL statement failed, but the transaction may still be alive and must be explicitly rolled back or committed.
Add explicit BEGIN TRY...BEGIN CATCH blocks to handle errors and roll back transactions gracefully.
A primary key violation occurs inside a larger transaction, terminating only the INSERT but leaving the transaction open.
10
1222
Lock request time out period exceeded.
Your query waited too long for a lock on a resource held by another process before timing out.
Tune the query to reduce lock duration, or temporarily increase the LOCK_TIMEOUT session setting.
A reporting query is blocked by a long-running nightly batch job.
Section 3: System & Configuration Errors
#
Error Code
Error Message
Cause
Fix/Solution
Example Scenario
11
701
There is insufficient system memory in resource pool ‘default’ to run this query.
SQL Server has run out of physical memory (RAM) or has hit its configured memory limit.
Increase the server’s physical RAM, or adjust the “max server memory” setting in SQL Server configuration.
An extremely complex query or a query with a huge memory grant runs on a server with limited RAM.
12
17883
Stack overflow on session ID X.
A poorly written recursive query (e.g., a Recursive CTE) or trigger failed to terminate, consuming all available stack memory.
Ensure recursive CTEs have a proper termination condition (WHERE clause in the anchor/recursive member) or use OPTION (MAXRECURSION N).
A recursive CTE runs indefinitely because the parent-child relationships form a circle.
13
18456
Login failed for user ‘X’.
The provided username/password is incorrect, the login is disabled, or the user is connecting from an unauthorized network.
Verify the username/password. Check the SQL Server error log for the exact reason (State code). Ensure the user is mapped to a database user.
An application uses hardcoded credentials that were recently changed on the server.
14
9002
The transaction log for database ‘X’ is full.
The transaction log file has grown to its maximum allowed size, and the database cannot record further transactions.
Take a Transaction Log Backup (if in FULL recovery model), or increase the size/autogrowth of the log file.
A huge data migration runs without proper log backup scheduling, filling the log disk.
15
3701
Cannot drop the table ‘X’ because it is being referenced by object ‘Y’.
Attempting to drop a table that is referenced by a Foreign Key constraint, View, Stored Procedure, or Function.
Drop the referencing object (e.g., the Foreign Key constraint) first, then drop the table.
Trying to drop the Customers table while the Orders table still has a Foreign Key relationship pointing to it.
Section 4: Query & Development Errors
#
Error Code
Error Message
Cause
Fix/Solution
Example Scenario
16
8134
Divide by zero error encountered.
An arithmetic operation attempts to divide a number by zero.
Use NULLIF() or CASE statements to check the divisor before performing the division.
Calculating a percentage where the total quantity is 0: Cost / TotalQuantity.
17
245
Conversion failed when converting the varchar value ‘X’ to data type int.
Attempting to convert a non-numeric string value (e.g., “N/A”) to a numeric data type (INT, DECIMAL).
Clean the data, or use TRY_CAST / TRY_CONVERT (SQL 2012+) to handle non-convertible data gracefully (returns NULL on failure).
Reading customer IDs from an import file where one row accidentally contains text.
18
4104
The multi-part identifier “X.Y” could not be bound.
A column or table reference is ambiguous (e.g., the same column name exists in both joined tables) or spelled incorrectly.
Use Table Aliases (e.g., E.Name) to explicitly specify which table the column belongs to.
Joining TableA and TableB, both of which have a column named ID, but selecting ID without prefixing it.
19
156
Incorrect syntax near the keyword ‘X’.
A syntax error in the T-SQL code, such as a missing parenthesis, comma, or keyword mismatch.
Carefully review the line near the error. Check documentation for the correct syntax of the surrounding statement (e.g., CREATE PROCEDURE).
Using WHERE Name = 'Alice' AND with no further condition.
20
207
Invalid column name ‘X’.
The column name used in the query does not exist in any of the tables referenced in the FROM clause.
Check the spelling of the column name against the table definition.
Typing CustomerName when the actual column name is CustName.
Section 5: Advanced & Indexing Errors
#
Error Code
Error Message
Cause
Fix/Solution
Example Scenario
21
8649
A limit on the total number of logical processors that can be used has been exceeded.
The Query Optimizer chose a highly parallel plan that exceeds the configured MAXDOP or the available CPU resources.
Reduce the complexity of the query or manually set MAXDOP to a lower value using a query hint.
A massive aggregation query tries to use all 64 cores simultaneously.
22
1907
Cannot create a clustered index on view ‘X’ because it is not schema bound.
Creating an Indexed View requires the view to be defined with WITH SCHEMABINDING to prevent changes to the underlying tables.
Add WITH SCHEMABINDING to the view definition, ensuring all objects are referenced with two-part names (e.g., dbo.TableName).
Attempting to create a materialized view for fast reporting without binding the view’s schema.
23
1934
UPDATE failed because the following objects have failed validation.
A dependency (like an index or constraint) on the table failed during the UPDATE operation, often related to computed columns.
Rebuild the index or check the computed column definition and its dependencies for inconsistencies.
An update violates a filtered index condition that the new value should satisfy.
24
824
SQL Server detected a logical consistency-based I/O error: incorrect checksum.
This indicates severe physical data corruption, meaning the data read from disk does not match the checksum recorded in the page header.
Restore the database from the last known good backup. Run DBCC CHECKDB to locate and confirm corruption.
A hardware failure, faulty disk controller, or bad memory caused the data page to be written incorrectly.
25
4145
An expression of non-boolean type specified in a context where a condition is expected.
Used a non-comparison or non-logical expression in a WHERE or HAVING clause.
Ensure the WHERE clause evaluates to a boolean (TRUE/FALSE), e.g., WHERE ColumnID = 1 instead of WHERE ColumnID.
Typing WHERE @ConditionVariable when @ConditionVariable is an INT, not a BIT or a comparison.
