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How Can I Sequentially Insert Data into Multiple Postgres Tables Using CTEs or a Temporary Table?
How Can I Sequentially Insert Data into Multiple Postgres Tables Using CTEs or a Temporary Table?
Jan 12, 2025 pm 02:35 PM
Using Postgres CTE to sequentially insert data in multiple tables
In Postgres, you can use data modifying common table expressions (CTE) to insert data into multiple tables with a single query. CTE provides a convenient way to define temporary result sets and manipulate data in a single query.
Use data to modify CTE
The following query demonstrates how to use CTE to sequentially insert data into three tables:
WITH ins1 AS (
INSERT INTO sample(firstname, lastname)
VALUES ('fai55', 'shaggk')
RETURNING id AS sample_id
), ins2 AS (
INSERT INTO sample1 (sample_id, adddetails)
SELECT sample_id, 'ss' FROM ins1
RETURNING user_id
)
INSERT INTO sample2 (user_id, value)
SELECT user_id, 'ss2' FROM ins2;
In this query:
- The first CTE,
ins1, inserts a row into thesampletable and returns the ID of the inserted row assample_id. - The second CTE,
ins2, uses theins1returned bysample_idto insert a row into thesample1table. It returns theuser_idof the inserted row. - The final
INSERTstatement inserts a row into theins2table using theuser_idreturned bysample2.
This approach allows you to chain multiple INSERT statements and reuse values ??returned from previous inserts.
Handling concurrent writes
If multiple sessions are inserting data at the same time, you must consider the possibility of concurrent writes. To do this, you can use the ON CONFLICT clause to specify the behavior when trying to insert a duplicate record.
Alternatives using temporary tables
As an alternative to using CTE, you can also create a temporary table to hold the intermediate data and then perform the inserts sequentially:
CREATE TEMP TABLE tmp AS SELECT * FROM sample; INSERT INTO sample1 (sample_id, adddetails) SELECT id, 'ss' FROM tmp; INSERT INTO sample2 (user_id, value) SELECT user_id, 'ss2' FROM tmp; DROP TABLE tmp;
This approach involves using a temporary table as the data source for subsequent inserts without directly linking the CTE.
By using a data modification CTE or temporary table, you can efficiently insert data into multiple tables with a single Postgres query, thus simplifying data insertion operations.
The above is the detailed content of How Can I Sequentially Insert Data into Multiple Postgres Tables Using CTEs or a Temporary Table?. For more information, please follow other related articles on the PHP Chinese website!
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