Step 4: Expand the Merged Table

Once the tables are combined, a new column will show up in the table.

• Click on
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• the expand icon
• Select the field you wish to bring
  • CustomerName
  • Country

Step 5: Outcome

Clarification: In this instance, the table is created by combining the Sales and Customer tables based on CustomerID.

Method 2: Merging Tables Using DAX

DAX, short for Data Analysis Expressions, is a robust language in Power BI utilized for custom computations and data aggregation. DAX can also be employed to merge tables.

Step 1: Import the dataset into Power BI

Navigate to Home>Get Data>Text/CSV

1. Customer Table:

2. Sales Table

Step 2: Access the Modelling Tab and input the formula below

Sales_Customer_Join = 

SELECTCOLUMNS (

    ADDCOLUMNS (

        Sales,

        "CustomerName", RELATED(Customer[CustomerName]),

        "Country", RELATED(Customer[Country])

    ),

    "SaleID", Sales[SaleID],

    "CustomerID", Sales[CustomerID],

    "Product", Sales[Product],

    "Amount", Sales[Amount],

    "SaleDate", Sales[SaleDate],

    "CustomerName", [CustomerName],

    "Country", [Country]

)

Clarification: In this instance, the table is created by merging the Sales and Customer tables based on CustomerID.

Performance Assessment: Power Query Join vs DAX Join

Both methods are valid and effective for concatenating rows; however, let’s examine a comparison of their performance.

Performance Factors When Merging Tables in Power BI

• Prior to merging two tables, attempt to eliminate unnecessary rows and columns to enhance performance.
• Ensure that the column used for joining the tables does not include any blank or null values.
• Eliminate duplicate entries before merging the tables, as this can produce inaccurate results.
• Opt for Left Join instead of Full Outer Join to avoid performance issues.
• Select only those columns necessary for the merge. Avoid unnecessary fields to reduce memory usage.

Recommended Practices for Merging Tables in Power BI

• Assign a name to your table: Naming your table while managing extensive and multiple tables can help prevent confusion.
• Verify Data Types: Always confirm the data types of the tables you intend to merge.
• Restrict the Number of Tables: Working on too many tables can impair performance; aim to minimize the number of tables to enhance efficiency.
• Employ DAX: For data transformation, using a DAX formula can optimize your data.

Troubleshooting Frequent Issues in Power BI

• Incompatible Data Types: Merging tables is impossible when columns have differing data types. You can rectify this error by transforming the data types of columns in Power Query.

• Duplicate entries: If duplicate entries exist in the column for merging, the operation will not provide accurate results. Resolve this issue by removing all duplicates in the Power Query Editor.

• Empty or Null values: If your table has empty values or NULL entries, the merged table will also include these. To prevent this, eliminate empty values or fill them using statistical methods like average, mean, mode, or median.

• Case Sensitivity: Ensure your records are uniformly uppercase or lowercase. You can address this by converting all records using Text.Upper() or Text.Lower().

• Incorrect Join Type: Using the wrong join type in tables can yield inaccurate results. Ensure that the appropriate join types are applied to obtain correct outcomes.

Final Thoughts

Merging tables in Power BI is an efficient method for handling data from various sources. It enables the integration of related information and the generation of more meaningful insights. By choosing the correct join method and pinpointing the appropriate common columns, you can guarantee data accuracy and performance. Properly merged tables enhance the cleanliness, speed, and manageability of the data model, improving report quality and facilitating superior business decisions.

For more insights into Power BI and its functionalities, explore this Power BI Course and check out Power BI Interview Questions curated by industry specialists.

How to Merge Tables in Power BI – FAQs

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