varchar

Postgresql – change the size of a varchar column to lower length

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I have a question about the ALTER TABLE command on a really large table (almost 30 millions rows). One of its columns is a varchar(255) and I would like to resize it to a varchar(40). Basically, I would like to change my column by running the following command: ALTER TABLE mytable ALTER COLUMN mycolumn TYPE … Read more

Is there a good reason I see VARCHAR(255) used so often (as opposed to another length)?

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In multiple courses, books, and jobs, I have seen text fields defined as VARCHAR(255) as kind of the default for “shortish” text. Is there any good reason that a length of 255 is chosen so often, other than being a nice round number? Is it a holdout from some time in the past when there … Read more

Changing the maximum length of a varchar column?

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I’m trying to update the length of a varchar column from 255 characters to 500 without losing the contents. I’ve dropped and re-created tables before but I’ve never been exposed to the alter statement which is what I believe I need to use to do this. I found the documentation here: ALTER TABLE (Transfact-SQL) however … Read more

What are the main performance differences between varchar and nvarchar SQL Server data types?

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I’m working on a database for a small web app at my school using SQL Server 2005. I see a couple of schools of thought on the issue of varchar vs nvarchar: Use varchar unless you deal with a lot of internationalized data, then use nvarchar. Just use nvarchar for everything. I’m beginning to see … Read more

SQL Server Text type vs. varchar data type [closed]

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