Troubleshooting String Binary Truncation Errors or Data type mismatch when updating SQL tables.

 Troubleshooting String Binary Truncation Errors in SQL Server

String binary truncation errors in Microsoft SQL Server can be frustrating to deal with, especially when you're dealing with large datasets or complex queries. These errors occur when a string value is too long to fit into a specified column, leading to data loss or corruption. Fortunately, there are steps you can take to identify and resolve these errors effectively.

1. Enable Trace Flags

The first step in troubleshooting string binary truncation errors is to enable trace flags to pinpoint which fields are causing the issue. This can be done using the DBCC TRACEON command in SQL Server. By enabling trace flags, you activate specific diagnostic features that can help identify the source of the error. I would recommend doing this on a test server to avoid any performance issues.

sql
DBCC TRACEON(460, -100);  -- Enable errors
DBCC TRACEOFF(460, -100); -- Disable errors

2. Extract Data into a Temporary Table

Once you've enabled trace flags, run your query to identify the offending column. If this does not work extract the data from your source table into a temporary table schema. This allows you to compare the field names and data types between the source table and the temporary table to identify any discrepancies.

sql
SELECT * INTO #temptable FROM YourSourceTable;

3. Compare Schemas for Variances

After extracting the data into a temporary table, compare the schemas of the source table and the temporary table for any variances in field names or data types. This can be done using a SQL query that retrieves column information from the INFORMATION_SCHEMA.COLUMNS system view.

sql
DECLARE @TableName1 NVARCHAR(128) = 'YourSourceTable'; 
DECLARE @TableName2 NVARCHAR(128) = '#temptable'; 
-- Compare field names and data types
WITH FieldComparison AS (
    SELECT
        @TableName1 AS TableName,
        COLUMN_NAME AS FieldName,
        DATA_TYPE AS DataType
    FROM
        INFORMATION_SCHEMA.COLUMNS
    WHERE
        TABLE_NAME = @TableName1

    UNION ALL

    SELECT
        @TableName2 AS TableName,
        COLUMN_NAME AS FieldName,
        DATA_TYPE AS DataType
    FROM
        INFORMATION_SCHEMA.COLUMNS
    WHERE
        TABLE_NAME = @TableName2
)
SELECT
    T1.TableName AS TableName1,
    T1.FieldName AS FieldName1,
    T1.DataType AS DataType1,
    T2.TableName AS TableName2,
    T2.FieldName AS FieldName2,
    T2.DataType AS DataType2,
	iif(T1.FieldName <> T2.FieldName, 'X', '') AS IsFieldMatch,
	iif(T1.DataType <> T2.DataType, 'X', '') AS IsDataTypeMatch
FROM
    (SELECT * FROM FieldComparison WHERE TableName = @TableName1) AS T1
FULL JOIN
    (SELECT * FROM FieldComparison WHERE TableName = @TableName2) AS T2
ON
    T1.FieldName = T2.FieldName
ORDER BY
    COALESCE(T1.FieldName, T2.FieldName);

4. Analyze Execution Plans

Additionally, you can analyze the execution plans of your queries to identify any implicit conversions that may be causing string binary truncation errors. This can be done by querying the sys.dm_exec_query_stats dynamic management view and examining query plans for implicit conversions.

sql
SELECT TOP(50) 
    DB_NAME(t.[dbid]) AS [Database Name], 
    t.text AS [Query Text],
    qs.total_worker_time AS [Total Worker Time], 
    qs.total_worker_time/qs.execution_count AS [Avg Worker Time], 
    qs.max_worker_time AS [Max Worker Time], 
    qs.total_elapsed_time/qs.execution_count AS [Avg Elapsed Time], 
    qs.max_elapsed_time AS [Max Elapsed Time],
    qs.total_logical_reads/qs.execution_count AS [Avg Logical Reads],
    qs.max_logical_reads AS [Max Logical Reads], 
    qs.execution_count AS [Execution Count], 
    qs.creation_time AS [Creation Time],
    qp.query_plan AS [Query Plan]
FROM 
    sys.dm_exec_query_stats AS qs WITH (NOLOCK)
    CROSS APPLY sys.dm_exec_sql_text(plan_handle) AS t 
    CROSS APPLY sys.dm_exec_query_plan(plan_handle) AS qp 
WHERE 
    CAST(query_plan AS NVARCHAR(MAX)) LIKE ('%CONVERT_IMPLICIT%')
    AND t.[dbid] = DB_ID()
ORDER BY 
    qs.total_worker_time DESC OPTION (RECOMPILE);

By following these steps and analyzing the results, you can effectively troubleshoot string binary truncation errors in SQL Server and ensure the integrity of your data.