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Table of Contents
MERGE ANOTHER TABLE
Category: Transform / Basic
Description
This action appends one or more columns from another table where the values in certain columns in both tables match.
There are three possible merge modes:
Lookup Mode
Retrieve the first matching combination from the other table. Any subsequent combinations are ignored.
Left Join Mode
Retrieve all matching combinations from the other table. This mode can increase the number of rows in the current table as rows are duplicated to hold any multiple matches from the second dataset.
Full Join Mode
Include all combinations of keys from both tables. Equivalent to the full outer join in SQL. This mode could potentially return very large datasets.
Limitations
The resulting table after Merge can't have more than 134,217,728 rows.
Use cases
- (Lookup Mode) Look up replacement values for common misspellings or abbreviations.
- (Left Join Mode) Blend in additional data from other tables into the primary dataset.
- (Full Join Mode) Combine two entire datasets to be cleaned and consolidated downstream.
Action settings
| Setting | Description |
|---|---|
| Add columns from table | Select table that will return columns to the current dataset where values match. |
| Where all these columns match | Select the columns within the current dataset (left drop-down) and the second dataset (right drop-down) where values will match. To define multi-columnar matches, use the Add more matching columns to select additional matching columns in each dataset. |
| Merge mode | Options: Lookup (for each row in this table, get any one matching row from the second table and ignore other matches), Left join (for each row in this table add all matching rows from the second table), Full join (add matching and non-matching rows from both tables). |
| Return columns | From the list, select the columns from the second dataset that will be appended to the current dataset. |
The reference to the second table will appear as a dotted line connecting this action to the second dataset in the application window.
Examples
Objective: Merge the "Outflow" column of Table 2 into Table 1 based on matching values in the "Rivers" columns in both tables.
Table 1: The longest rivers in the world
| River | Length (km) | Continent |
|---|---|---|
| Nile | 6650 | Africa |
| Amazon | 6400 | South America |
| Yangtze | 6300 | Asia |
| Mississippi | 6275 | North America |
Table 2: The outflow
| River | Outflow |
|---|---|
| Nile | Mediterranean |
| Amazon | Atlantic Ocean |
| Yangtze | East China Sea |
| Mississippi | Gulf of Mexico |
Action parameters:
Add columns from table: Table 2
Where values in the Table 1 "River" column match values in the Table 2 "River" column
Merge mode: Left join (add all matching rows from Table 2 to Table 1)
Return column: Outflow
Result:
| River | Length (km) | Continent | Outflow |
|---|---|---|---|
| Nile | 6650 | Africa | Mediterranean |
| Amazon | 6400 | South America | Atlantic Ocean |
| Yangtze | 6300 | Asia | East China Sea |
| Mississippi | 6275 | North America | Gulf of Mexico |