SQL column added twice during INNER JOIN-CodePudding

I am trying to join two tables from a database; energyImport and sunAlt.

energyImport has three columns: timestamp_id, energy, duration.

sunAlt has two columns: timestamp_id, altitude

I am doing an inner join on these two tables using the SQL:

SELECT * 
FROM energyImport
INNER JOIN sunAz ON sunAz.timestamp_id = energyImport.timestamp_id;

The output from this is:

timestamp_id,duration,energy,timestamp_id,altitude
1601769600,1800,81310,1601769600,0.0
1601771400,1800,78915,1601771400,0.0
1601773200,1800,78305,1601773200,0.0

The problem is that the timestamp_id column is repeated. How can I join these columns and only include the first timestamp_id?

CodePudding user response：

Replace the * with

energyImport.timestamp_id,energyImport.duration, energyImport.energy,
sunAz.altitude

CodePudding user response：

Either you specify the columns that you want in the results:

SELECT e.timestamp_id, e.duration, e.energy, s.altitude 
FROM energyImport e INNER JOIN sunAz s
ON s.timestamp_id = e.timestamp_id;

Or, use NATURAL instead of INNER join, so that the join is based on the columns(s) with the same names of the 2 tables (if this fits your requirement), because NATURAL join returns only 1 of each pair of these columns:

SELECT *
FROM energyImport NATURAL JOIN sunAz;

See the demo.