If you worked in same job and place but different company, how should you put that on your resume?

List them together. That way it shows that you've been at the same job for a while with continuous job experience. Listing them separately might make it look like you left and came back, or went to a different job.

An example of how to list them would be:

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September 2000 to September 2011

Company B (formerly known as Company A)

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This shows that you have eleven continuous years of experience in the same position with the company(s).

If you listed them like this:

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May 2005 to September 2011

Company B

September 2000 to May 2005

Company A

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it could look like you switched jobs, which is not as good as staying at your current job.

Longevity at a job speaks volumes to future employers. They likely desire loyalty, and your staying with a company that has switched hands demonstrates loyalty, shows flexibility, and makes you desirable as an employee because the new company valued you enough to keep you on instead of bringing someone else in for your position.