Why doesn't self condensation occur in acetoacetic ester synthesis So, I came across a quite versatile method to synthesize aldehydes and ketones, its called the Acetoacetic ester synthesis. 

Suppose I need some 2-pentanone. So to synthesize it via this method I can do this 



But I'm more worried about adding a base to Acetoacetic ester. Won't self condensation occur between two molecules of Acetoacetic ester like this?



If it occurs how do we minimize it? If it doesn't then why?

Any help will be appreciated.
Self-condensation is typically not an issue with 1,3-dicarbonyl compounds, such as the one in your question. Why? Due to their acidity ($\mathrm{p}K_\mathrm{a}$ around 9 to 11), most 1,3-dicarbonyls exist in their enolate form in solution. Therefore, there is very little of the original electrophilic 1,3-dicarbonyl which the enolate can attack. Hence, the amount of self-condensation taking place is relatively little and usually not a concern.