coalesce

verb5

1. •
   To join into a single mass or whole.

   • The droplets coalesced into a puddle.
2. •
   To form from different pieces or elements.

   • The puddle coalesced from the droplets as they ran together.
3. •
   To bond pieces of metal into a continuous whole by liquefying parts of each piece, bringing the liquids into contact, and allowing the combined liquid to solidify.
4. •
   To merge, to intermingle freely.

   • It was not a wise thing to enter a close clique, my good madam, until you had examined both them and yourself, and considered how far you were likely to coalesce. — 1842
5. •
   To convert a null value to a defined value.

   • You can improve the display by coalescing the ID columns. As I note in Chapter 9, the COALESCE expression takes on the value of the first non-null value in a list of values. — 2018