Power BI: types of table joins
When merging queries, one must consider the type of #merge (the join kind), as depending on that a result can be totally different. Currently, there are 6 types of join kinds within the merge queries function and we are going to take a closer look at them.
Left outer join: merges all rows from the first query and only matching from the second. Probably one of the most popular join types. This type of join is same as the Excel Vlookup function.
Right outer join: merges all rows from the second and only matching from the first. This type of join mirrors the previous one and does the same join as the left outer but keeping all rows from the right query.
Full outer join: merges all rows from both queries. Use this type of join when it is important to keep all rows from both tables (either matching or non-matching). For those who are familiar with SQL, this join is same as “Union All” function.
Inner join: merges only matching rows. This type of join only merges matching rows, meaning there will not be any records with null values. Serves well when there is a need to build a third table, which has items that exist in two merging queries.
Anti joins: bring in data from only either the first query (left anti) or the second query (right anti). The left anti join brings in rows that in the first table and do not match with the second table. The right anti join does exactly the same thing, but for the second table. The anti joins are helpful when finding rows that only exist in one table and not the other one.
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Keywords:
#PowerBI #PowerQuery
#table #join #merge