Align region names to one standard

Combine sido, sigungu, and dong into a composite key that connects tables safely.

Question for this chapter

How can a dong be connected without confusing it with a same-named dong elsewhere?

Why this matters now

A name such as 중앙동 can occur in several sigungu. Joining on the dong name alone can mix regions. sido|sigungu|dong turns the complete regional address into the key.

Try it

Open Floating Population (floating_population) and Resident Population (residents_population) in COVID-19 Data Collection. In Schema, verify that sido, sigungu, and dong are all Text.

Sido, sigungu, and dong schema in Floating Population — Inspect the three regional field names and types.

Sido, sigungu, and dong schema in Resident Population — Verify that Resident Population uses the same three fields and types.

Open Population Data Join Pipeline. Verify that the two inputs feed the join code and that the code feeds Dong Information (region_dong), then select Run now.

Pipeline joining two population datasets by regional key — Verify both inputs, join code, and output before running.

Success looks like this

The run ends successfully and Dong Information (region_dong) has a new version.

Interpret the result

서울특별시|노원구|중계4동 contains all three levels and cannot collide with a same-named dong elsewhere. The full regional hierarchy—not one name—is the join key.

Observation	Interpretation	Operational use
Both inputs contain `sido`, `sigungu`, and `dong`.	The tables are ready for one hierarchy.	Apply the same join to population, patient, and facility data.
All three fields are Text.	Type differences are less likely to drop a match.	Verify the schema contract before running.
Both population fields appear in one `region_dong` row.	The composite key connected the same area.	Use the row for regional differences and rates.

Do not judge a join only by its row count. A region present only on the left can disappear. In operations, compare unique-region counts and list unmatched regions before and after the join.

Next decision

The regions now connect correctly. Next, distinguish the meaning of resident and floating population in the same row.