`information_schema.global_variables.*`

show items implemented by

any at least two only one database all databases

relation	column	mysql	mariadb	tidb	postgres	cockroachdb	mssql
`global_variables`
	`variable_name`	`VARCHAR NOT NULL`: 5.7	`VARCHAR NOT NULL`: 10.2-10.7	unsupported	unsupported	unsupported	unsupported
	`variable_value`	`VARCHAR NULL`: 5.7	`VARCHAR NOT NULL`: 10.2-10.7	unsupported	unsupported	unsupported	unsupported