IANAL. If all they hired you to do is make a random database, and you do so in a really efficient manner, then you still own the right to use your skills to ma

IANAL. If all they hired you to do is make a random database, and you do so in a really efficient manner, then you still own the right to use your skills to make a really efficient database for others. If they hire you to make a specific database, and you make it really efficient, then they probably own the rights to such a specific database, but you still retain the rights to make other kinds of databases in a really efficient manner. If they hire you to develop database to a certain degree of efficiency, then they might own the techniques you used to make it efficient, but this should be blatantly spelled out in your employment contract, and you should have been appropriately compensated for the inability to use this particular skillset in the future.