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REPLACE INTO

Introduced: v1.1.55

REPLACE INTO either inserts a new row into a table or updates an existing row if the row already exists with the following:

  • Direct values
  • Query results
  • Staged data files

When a row with the specified conflict key already exists in the table, REPLACE INTO will replace that existing row with the new data provided. However, if the row does not exist, a new row will be inserted into the table with the specified data.

atomic operations

Databend ensures data integrity with atomic operations. Inserts, updates, replaces, and deletes either succeed completely or fail entirely.

Syntax​

REPLACE INTO <table_name> [ ( <col_name> [ , ... ] ) ]
    ON (<CONFLICT KEY>) ...

What is Conflict Key?​

The conflict key is a column or combination of columns in a table that uniquely identifies a row and is used to determine whether to insert a new row or update an existing row in the table using the REPLACE INTO statement. It can be any column or combination of columns with a unique constraint, not just the primary key(Databend doesn't have primary key).

For example, in a table called "employees" with a unique constraint on the "employee_email" column, you can use the "employee_email" column as the conflict key in the REPLACE INTO statement:

REPLACE INTO employees (employee_id, employee_name, employee_salary, employee_email) ON (employee_email)
VALUES (123, 'John Doe', 50000, 'john.doe@example.com');

Examples​

Here are some examples that show how to use the REPLACE INTO statement in Databend:

Replace with Direct Values​

CREATE TABLE employees(id INT, name VARCHAR, salary INT);
REPLACE INTO employees (id, name, salary) ON (id)
VALUES (1, 'John Doe', 50000);
SELECT  * FROM Employees;
+------+----------+--------+
| id   | name     | salary |
+------+----------+--------+
|    1 | John Doe |  50000 |
+------+----------+--------+

Replace with Query Results​

In this case, the data to be inserted or updated comes from a temporary table called temp_employees:

CREATE TABLE employees(id INT, name VARCHAR, salary INT);
-- Create a temp stage table
CREATE TABLE temp_employees(id INT, name VARCHAR, salary INT);
INSERT INTO temp_employees (id, name, salary) VALUES (1, 'John Doe', 60000);

REPLACE INTO employees (id, name, salary) ON (id)
SELECT id, name, salary FROM temp_employees WHERE id = 1;
SELECT  * FROM Employees;
+------+----------+--------+
| id   | name     | salary |
+------+----------+--------+
|    1 | John Doe |  60000 |
+------+----------+--------+

Replace with Staged Files​

Below is an example that demonstrates how to use staged files for updating data with a REPLACE INTO statement. It's important to note that the REPLACE INTO functionality with staged files is only available when using Databend's HTTP handler.

First, create a table called "sample":

CREATE TABLE sample
(
    Id      INT,
    City    VARCHAR,
    Score   INT,
    Country VARCHAR DEFAULT 'China'
);

Then, create an internal stage and upload a sample CSV file called sample_3_replace.csv to the stage:

CREATE STAGE s1 FILE_FORMAT = (TYPE = CSV);
curl -u root: -H "stage_name:s1" -F "upload=@sample_3_replace.csv" -XPUT "http://localhost:8000/v1/upload_to_stage"

{"id":"b8305187-c816-4bb5-8350-c441b85baaf9","stage_name":"s1","state":"SUCCESS","files":["sample_3_replace.csv"]}   
LIST @s1;

name                |size|md5|last_modified                |creator|
--------------------+----+---+-----------------------------+-------+
sample_3_replace.csv|  83|   |2023-06-12 03:01:56.522 +0000|       |

Use REPLACE INTO to insert data from the staged CSV file through the HTTP handler:

tip

You can specify the file format and various copy-related settings with the FILE_FORMAT and COPY_OPTIONS available in the COPY INTO command. When purge is set to true, the original file will only be deleted if the data update is successful. 

curl -s -u root: -XPOST "http://localhost:8000/v1/query" --header 'Content-Type: application/json' -d '{"sql": "REPLACE INTO sample (Id, City, Score) ON(Id) VALUES", "stage_attachment": {"location": "@s1/sample_3_replace.csv", "copy_options": {"purge": "true"}}}'

{"id":"92182fc6-11b9-461b-8fbd-f82ecaa637ef","session_id":"f5caf18a-5dc8-422d-80b7-719a6da76039","session":{},"schema":[],"data":[],"state":"Succeeded","error":null,"stats":{"scan_progress":{"rows":5,"bytes":83},"write_progress":{"rows":5,"bytes":277},"result_progress":{"rows":0,"bytes":0},"total_scan":{"rows":0,"bytes":0},"running_time_ms":143.632441},"affect":null,"stats_uri":"/v1/query/92182fc6-11b9-461b-8fbd-f82ecaa637ef","final_uri":"/v1/query/92182fc6-11b9-461b-8fbd-f82ecaa637ef/final","next_uri":"/v1/query/92182fc6-11b9-461b-8fbd-f82ecaa637ef/final","kill_uri":"/v1/query/92182fc6-11b9-461b-8fbd-f82ecaa637ef/kill"}

Verify the inserted data:

SELECT * FROM sample;

id|city       |score|country|
--+-----------+-----+-------+
 1|'Chengdu'  |   80|China  |
 3|'Chongqing'|   90|China  |
 6|'HangZhou' |   92|China  |
 9|'Changsha' |   91|China  |
10|'Hong Kong'|   88|China  |