how we can perform left and right join in gooddata maql

Only in GoodData CN/cloud, we recently added FOR EACH feature providing related functionality: https://www.gooddata.com/developers/cloud-native/doc/2.3/create-metrics/maql/time/for-each/

See https://community.gooddata.com/data-models-kb-articles-46/how-to-display-null-or-missing-values-98 for some tip how to display missing values in GoodData Platform. GoodData Cloud product now offers also “show missing values” feature which can be used in addition to FOR EACH keyword mentioned above (see release notes).