${\mathrm{BaCl}}_2+{\mathrm{Na}}_2{\mathrm{SO}}_4\to {\mathrm{BaSO}}_4+2\mathrm{NaCl}$
i) Decomposition reaction               
ii) Displacemnent reaction 
iii) Precipitation reaction                 
iv) Double displacement reaction

This is an example of double displacement reaction in which ion exchange takes place and thus barium sulfate is formed as a precipitate and sodium chloride as a aqueous solution. So this  is also precipitation reaction