Inserting Data into a Table (PostgreSQL)

Now that our cities table is ready, the next step is to add data into it.

We want to store information about these cities:

• Tokyo

• Delhi

• Shanghai

• Sao Paulo

Along with:

• country

• population

• area

To do this, we will use SQL again.

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Using INSERT INTO

To add data into a table, PostgreSQL provides the INSERT INTO command.

The basic structure looks like this:

insert into table_name (column1, column2, ...)
values (value1, value2, ...);

Let’s apply this to our cities table.

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Inserting a Single Row

Here is the SQL to insert Tokyo into the cities table:

insert into cities (name, country, population, area)
values ('Tokyo', 'Japan', 38505000, 8223);

Important things to notice

• insert into → tells PostgreSQL we want to add data

• cities → the table name

• (name, country, population, area) → columns we are providing values for

• values → keyword before actual data

• Text values use single quotes

• Numbers do not use quotes

After running this query, PostgreSQL will respond with something like:

Insert successful — 1 row added

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About the Semicolon (;)

You’ll notice a semicolon at the end of the SQL statement.

Technically:

• some tools allow running SQL without it

• but it is part of SQL standard

Best practice:
👉 Always end SQL statements with a semicolon, especially when writing multiple queries.

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Column Order Matters

The order of columns must match the order of values.

For example:

insert into cities (name, country, population, area)
values ('Tokyo', 'Japan', 38505000, 8223);

Here:

• Tokyo → goes into name

• Japan → goes into country

• 38505000 → goes into population

• 8223 → goes into area

If you change the column order, the values must change too.

Otherwise, PostgreSQL will either:

• throw an error

• or insert wrong data into wrong columns

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Inserting Multiple Rows at Once

Instead of running INSERT again and again, PostgreSQL allows us to insert multiple rows in one query.

This is done by separating value groups with commas.

Example

insert into cities (name, country, population, area)
values
  ('Delhi', 'India', 28125000, 2240),
  ('Shanghai', 'China', 22125000, 4015),
  ('Sao Paulo', 'Brazil', 20935000, 3043);

What’s happening here?

• Each set of parentheses represents one row

• All rows are inserted in a single SQL statement

• Much faster and cleaner than multiple inserts

After running this, PostgreSQL will respond with:

Insert successful — 3 rows added

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What We Have So Far

At this point:

• the cities table exists

• it has data inside it

• each city is stored as a separate row

Now our table actually contains meaningful information.

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What’s Next?

The next step is to retrieve data from the table.

In the next blog, we’ll learn how to use SELECT to:

• read all cities

• view specific columns

• fetch data from the database