SQL: Count value une a field
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I would like to know if it is possible to have this kind of schema:

Table 1: Field1 | Field4 | Field3
         Field1 | Field4 | Field3 
         Field1 | Field4 | Field3

Table 2: Field4 | Field5(Number of Field3)


To explain the schema, my tables have a similar field, (number4) 

And my real question is: 

Can i have a dynamic database where the field5 would be the count of field 3 where Table1.field4 = Table2.field4  Or should i change it by hand with php? 


Thanks in advance.


