Learn in the textbookDatabase and DBMS Basics, and Types of NoSQL
DefinitionA key-value store (キーバリューストア) is a NoSQL type that saves a key, used to look up data, together with its content, the value, as one pair.
ExplanationSpecify a key and the one matching value comes back; the mechanism is that simple, so reads and writes are fast. Because the DBMS does not define the form of what is inside a value, it is a poor fit for searches that use a field inside the value as the condition.
AnalogyIt is like a cloakroom that works with numbered tags. Give the tag number and your item comes right out, but you cannot ask the staff to find it by what is inside.
Memory hookIt has the same shape as a dictionary entry: headword, then definition. The headword is the key and the definition is the value.