PostgreSQL: Copy data into another column with different data type

Question

I am new to PostgreSQL. Now I have a table containing several columns. There are two columns I'm dealing with: city and city_bak. city_bak is of type integer and stores data of cities. The city column is currently null and is of type integer[]. What I want to do is to copy data from city_bak into city. Like this:

[PREVIOUS]

 |  city  |  city_bak  |
 |        |    100     |
 |        |    700     |
 |        |    1800    |

[AFTER]

 |  city  |  city_bak  |
 | {100}  |    100     |
 | {700}  |    700     |
 | {1800} |    1800    |

Normally when the two columns are of the same data type, I'd use

UPDATE {table_name} SET city=city_bak

But now they are different. How can I copy data in this scenario? Thanks in advance.

Gordon Linoff · Accepted Answer · 2017-02-13 03:45:25Z

2

Is this what you want?

UPDATE {table_name}
    SET city = ARRAY[city_bak];

answered Feb 13, 2017 at 3:45

Gordon Linoff

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1 Comment

joe wong Over a year ago

That's it! Thank you!

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