MQL4 is a high-level, object-oriented language based on C++ and a strong focus on flexibility. That’s what allows it to develop complex programs with a huge number of calculations. This, in combination with built-in functions for managing trading orders, is what explains why this language is mostly used for trading robots, indicators, scripts, and libraries for the MetaTrader 4 platform. 

Query languages, data query languages or database query languages (DQLs) are computer languages used to make queries in databases and information systems. A well known example is the Structured Query Language (SQL).