How to merge data from multiple tables into one table?

1 year ago
Ava Mitchell
2 minutes

There are several ways to merge data from multiple tables into one table, with the most common methods being using SQL statements or data processing tools. Here are some common methods:

  1. Using the JOIN operator in SQL statements: you can use INNER JOIN, LEFT JOIN, RIGHT JOIN, and other operators to connect multiple tables based on their common columns. For example:
SELECT * 
FROM table1
INNER JOIN table2 ON table1.id = table2.id;
  1. Using the UNION operator: you can combine data from multiple tables into one table, as long as the number of columns and data types for each table match. For example:
SELECT * FROM table1
UNION
SELECT * FROM table2;
  1. By using a subquery, you can combine data from multiple tables into one table. For example:
SELECT * 
FROM table1
WHERE id IN (SELECT id FROM table2);
  1. Utilizing data processing tools like Python’s Pandas library, multiple tables of data can be combined into a single table using functions such as merge and concat. For example:
import pandas as pd

df1 = pd.read_csv('table1.csv')
df2 = pd.read_csv('table2.csv')

merged_df = pd.merge(df1, df2, on='id')

One can choose a suitable method to merge multiple tables into one table based on specific circumstances.

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