When a structure is read in using the standard thermodynamic format, the third line gives the atom counts for the structure. The purpose of using atom counts is to facilitate the substructure search.
The AtomCounts mySQL table has the following elements::
AtomCountKey: A unique key for the element
Molecule: This is the name of the molecule
AtomSymbol: The is the atomic name
AtomCount: The number of the type of atom
A particular molecule has several elements, one for each atom, within a molecule. For example the 2-butanone has three elements, corresponding to the three atoms, C, H and O:
select * from AtomCounts where Molecule='2-butanone';
+--------------+------------+------------+-----------+
| AtomCountKey | Molecule | AtomSymbol | AtomCount |
+--------------+------------+------------+-----------+
| 2-butanone-C | 2-butanone | C | 4 |
| 2-butanone-O | 2-butanone | O | 1 |
| 2-butanone-H | 2-butanone | H | 8 |
+--------------+------------+------------+-----------+