${\mathrm{CuSO}}_{4\left(\mathrm{aq}\right)}+2{\mathrm{NaOH}}_{\left(\mathrm{aq}\right)}\to \mathrm{Cu}{\left(\mathrm{OH}\right)}_{2\left(\mathrm{s}\right)}+{\mathrm{Na}}_2{\mathrm{SO}}_{4\left(\mathrm{aq}\right)}$ This reaction is an example for

In the given reaction, the product $\mathrm{Cu}{\left(\mathrm{OH}\right)}_{2\left(\mathrm{s}\right)}$ is insoluble in water. Hence, it is a precipitation reaction. In the given chemical reaction, the reactants $\mathrm{Cu}{\left(\mathrm{OH}\right)}_{2\left(\mathrm{s}\right)} \& {\mathrm{NaOH}}_{\left(\mathrm{aq}\right)}$ both are involving in decomposition as well as displacement reaction.

According to electro chemical series, sodium (Na) and (Cu) Mutual exchanges, therefore it is a double displacement reaction. In the above reaction, there is mutual exchange of ions is taking place. So, it is a double decomposition reaction also.