如何在SSIS数据流中转置字符串？行转列及列内拼接串转置方案

Hey there! I get it—dealing with millions of rows in SSIS can be tricky, especially when the built-in Pivot transform doesn't fit your use case. Let's break down solutions for both of your requirements, with performance in mind since you're working with large datasets.

The Pivot transform is designed for aggregating numeric values, not merging string rows—so it's no surprise it didn't work here. Here are two reliable approaches:

Option 1: Preprocess in the Source Database (Recommended for Large Datasets) #

If your data comes from a database like SQL Server, handling the row-to-column merge directly in your source query is way more efficient than doing it in SSIS. The database engine is optimized for these kinds of aggregations, which will save you memory and processing time with millions of rows.

For SQL Server 2017+ (STRING_AGG) #

Use the built-in STRING_AGG function to concatenate rows into a single string per group:

SELECT 
    YourGroupingKeyColumn,
    STRING_AGG(YourStringColumn, ', ') AS CombinedSingleColumn
FROM YourSourceTable
GROUP BY YourGroupingKeyColumn

Replace YourGroupingKeyColumn with the column that defines which rows belong together, and adjust the delimiter (, ) to match your needs.

For Older SQL Server Versions (FOR XML PATH) #

If you're on a version before 2017, use the FOR XML PATH trick to achieve the same result:

SELECT 
    t1.YourGroupingKeyColumn,
    STUFF(
        (SELECT ', ' + t2.YourStringColumn 
         FROM YourSourceTable t2 
         WHERE t2.YourGroupingKeyColumn = t1.YourGroupingKeyColumn 
         FOR XML PATH(''), TYPE).value('.', 'NVARCHAR(MAX)'), 
        1, 2, ''
    ) AS CombinedSingleColumn
FROM YourSourceTable t1
GROUP BY t1.YourGroupingKeyColumn

The STUFF function removes the leading delimiter from the concatenated string.

Option 2: Use an SSIS Script Component (If You Need to Process in the Data Flow) #

If you must handle this within the SSIS data flow, use an asynchronous Script Component to collect and merge rows per group. This requires a bit of custom code, but it's flexible.

Step-by-Step Setup: #

1. Drag a Script Component into your data flow, select Transformation as the type.
2. In the Script Component Editor:
   • Go to the Input Columns tab and check your grouping key column and the string column you want to merge.
   • Go to the Inputs and Outputs tab:
     • Set SynchronousInputID to None (this makes it an asynchronous component, meaning it can output fewer rows than it receives).
     • Add a new output (e.g., MergedOutput) and add two columns: your grouping key column, and a new string column (e.g., CombinedString).
3. Edit the script (C# example below):

using System.Collections.Generic;
using System.Text;

public class ScriptMain : UserComponent
{
    // Use a dictionary to cache grouping keys and their merged strings
    private Dictionary<int, StringBuilder> _groupCache = new Dictionary<int, StringBuilder>();

    public override void Input0_ProcessInputRow(Input0Buffer Row)
    {
        int groupKey = Row.YourGroupingKeyColumn;
        string stringValue = Row.YourStringColumn;

        if (!_groupCache.ContainsKey(groupKey))
        {
            _groupCache.Add(groupKey, new StringBuilder(stringValue));
        }
        else
        {
            _groupCache[groupKey].Append(", ").Append(stringValue);
        }
    }

    public override void PostExecute()
    {
        base.PostExecute();
        // Output the merged results after processing all input rows
        foreach (var group in _groupCache)
        {
            MergedOutputBuffer.AddRow();
            MergedOutputBuffer.YourGroupingKeyColumn = group.Key;
            MergedOutputBuffer.CombinedString = group.Value.ToString();
        }
    }
}

• Adjust the dictionary's key type if your grouping key is a string (change int to string).
• For very large datasets, ensure your SSIS server has enough memory to handle the cache—if your grouping count is extremely high, consider breaking the data into batches.

For your second requirement (turning a column like "A,B,C" into separate rows for A, B, C), again, database-side processing is preferred for performance. But here's how to do it both ways:

Option 1: Preprocess in the Source Database (Recommended) #

For SQL Server 2016+ (STRING_SPLIT) #

Use the built-in STRING_SPLIT function to split the concatenated string into rows:

SELECT 
    YourIDColumn,
    TRIM(value) AS SplitStringValue
FROM YourSourceTable
CROSS APPLY STRING_SPLIT(YourConcatenatedColumn, ',')

The TRIM function removes any leading/trailing spaces from split values, and CROSS APPLY joins the split results back to the original row.

For Older SQL Server Versions (Custom Split Function) #

If you're on an older version, create a custom split function first:

CREATE FUNCTION dbo.SplitConcatenatedString
(
    @InputString NVARCHAR(MAX),
    @Delimiter CHAR(1)
)
RETURNS @SplitResults TABLE (Value NVARCHAR(MAX))
AS
BEGIN
    DECLARE @StartIndex INT = 1;
    DECLARE @EndIndex INT;

    -- Add delimiter to end if missing, to avoid missing the last value
    IF RIGHT(@InputString, 1) <> @Delimiter
    BEGIN
        SET @InputString = @InputString + @Delimiter;
    END

    WHILE CHARINDEX(@Delimiter, @InputString) > 0
    BEGIN
        SET @EndIndex = CHARINDEX(@Delimiter, @InputString);
        INSERT INTO @SplitResults(Value)
        SELECT SUBSTRING(@InputString, @StartIndex, @EndIndex - @StartIndex);
        SET @InputString = SUBSTRING(@InputString, @EndIndex + 1, LEN(@InputString));
    END

    RETURN;
END

Then use it in your query:

SELECT 
    YourIDColumn,
    TRIM(Value) AS SplitStringValue
FROM YourSourceTable
CROSS APPLY dbo.SplitConcatenatedString(YourConcatenatedColumn, ',')

Option 2: SSIS Script Component (Data Flow Processing) #

To split the string into rows within SSIS, use an asynchronous Script Component (since we're generating multiple output rows from one input row).

Step-by-Step Setup: #

1. Drag a Script Component into your data flow, select Transformation as the type.
2. In the Script Component Editor:
   • Go to the Input Columns tab and check your ID column (to keep context) and the concatenated string column.
   • Go to the Inputs and Outputs tab:
     • Set SynchronousInputID to None.
     • Add a new output (e.g., SplitOutput) with two columns: your ID column, and a new string column (e.g., SplitStringValue).
3. Edit the script (C# example):

using System;

public class ScriptMain : UserComponent
{
    public override void Input0_ProcessInputRow(Input0Buffer Row)
    {
        // Skip null or empty values
        if (Row.YourConcatenatedColumn_IsNull || string.IsNullOrWhiteSpace(Row.YourConcatenatedColumn))
        {
            return;
        }

        // Split the string using comma as delimiter, remove empty entries
        string[] splitValues = Row.YourConcatenatedColumn.Split(new[] { ',' }, StringSplitOptions.RemoveEmptyEntries);
        
        foreach (string val in splitValues)
        {
            SplitOutputBuffer.AddRow();
            SplitOutputBuffer.YourIDColumn = Row.YourIDColumn;
            SplitOutputBuffer.SplitStringValue = val.Trim();
        }
    }
}

This will generate one output row for each split value, preserving the original ID to maintain context.

Quick Performance Note #

For millions of rows, always prioritize database-side processing over SSIS script components. Databases are built to handle large-scale data transformations efficiently, whereas SSIS scripts rely on server memory and can be slower for huge datasets. If you have to use SSIS scripts, make sure to test with a subset of data first and adjust memory settings as needed.

内容的提问来源于stack exchange，提问作者user3463579