How create concat array within a variable for lookup activity output, iterated within foreach loop

As you don't have any duplicates in your table, you can union the lookup output array in each iteration with its previous iteration lookup output array to get the final array.

Here, for sample instead of 5000 rows, I took 4 rows as limit where my table consists of total 16 rows and my id column is equivalent to your OffsetValue column.

First, create two array variables temp_arr and res_arr with empty default values like below.

I have followed same approach and same queries as yours till the second lookup activity.

Inside For-Each, after second lookup activity, take a set variable activity for temp_arr and give @variables('res_arr') to it.

Next, take another set variable activity for res_arr variable and give the below expression.

@union(variables('temp_arr'),activity('Lookup2').output.value) 

In ADF, self-referencing variables is not supported, that is the reason why the temp_arr variable was used.

At the end of the For-loop, the result final array will be stored in the res_arr variable.

Result:

UPDATE:

Your activities are running parallelly inside For-Each. You need to check the Sequential check box in the For-Each activity to run the activities sequentially.

The output array will be stored in the res_arr variable. If you want to access the array after For-Each, you need to use this array.

My pipeline JSON for your reference:

Change the datasets name and query and activity names as per your requirement and use it.

{ "name": "lookup concat pipeline", "properties": { "activities": [ { "name": "Lookup1", "type": "Lookup", "dependsOn": [], "policy": { "timeout": "0.12:00:00", "retry": 0, "retryIntervalInSeconds": 30, "secureOutput": false, "secureInput": false }, "userProperties": [], "typeProperties": { "source": { "type": "AzureSqlSource", "sqlReaderQuery": "SELECT COUNT(*) as TotalCount FROM lookup1", "queryTimeout": "02:00:00", "partitionOption": "None" }, "dataset": { "referenceName": "lookup_table", "type": "DatasetReference" }, "firstRowOnly": true } }, { "name": "ForEach1", "type": "ForEach", "dependsOn": [ { "activity": "Lookup1", "dependencyConditions": [ "Succeeded" ] } ], "userProperties": [], "typeProperties": { "items": { "value": "@range(0, add(div(activity('Lookup1').output.firstRow.TotalCount, 4), 1))", "type": "Expression" }, "isSequential": true, "activities": [ { "name": "Lookup2", "type": "Lookup", "dependsOn": [], "policy": { "timeout": "0.12:00:00", "retry": 0, "retryIntervalInSeconds": 30, "secureOutput": false, "secureInput": false }, "userProperties": [], "typeProperties": { "source": { "type": "AzureSqlSource", "sqlReaderQuery": { "value": "SELECT * FROM lookup1 ORDER BY id OFFSET @{mul(int(item()), 4)} ROWS FETCH NEXT 4 ROWS ONLY", "type": "Expression" }, "queryTimeout": "02:00:00", "partitionOption": "None" }, "dataset": { "referenceName": "lookup_table", "type": "DatasetReference" }, "firstRowOnly": false } }, { "name": "temp_arr", "type": "SetVariable", "dependsOn": [ { "activity": "Lookup2", "dependencyConditions": [ "Succeeded" ] } ], "policy": { "secureOutput": false, "secureInput": false }, "userProperties": [], "typeProperties": { "variableName": "temp_arr", "value": { "value": "@variables('res_arr')", "type": "Expression" } } }, { "name": "union temp and and lookup array", "type": "SetVariable", "dependsOn": [ { "activity": "temp_arr", "dependencyConditions": [ "Succeeded" ] } ], "policy": { "secureOutput": false, "secureInput": false }, "userProperties": [], "typeProperties": { "variableName": "res_arr", "value": { "value": "@union(variables('temp_arr'),activity('Lookup2').output.value)", "type": "Expression" } } } ] } } ], "variables": { "temp_arr": { "type": "Array" }, "res_arr": { "type": "Array" } }, "annotations": [], "lastPublishTime": "2024-05-29T04:16:16Z" }, "type": "Microsoft.DataFactory/factories/pipelines" }