Joining data
The join operation is used to merge entries from a data source to another using a common column as a key to pair the data correctly. The concept of joining is commonly seen in database technologies, in which we also see the different types of joins, such as inner join, outer join, left join, and right join. These joins are better represented in the following diagram:
Figure 4.1 – Inner, outer, left, and right joins
When joining data, we must identify the key column for both dataframes. Let's look at an example:
df_a = op.create.dataframe({
    "id": [143, 225, 545, 765, 152],
    "name": ["Alice", "Bob", "Charlie", "Dan", "Frank"]
})
df_b = op.create.dataframe({
    "id": [225, 545, 765, 152, 329],
    "city": ["Bradford", "Norwich", "Bath...
