Add SQL language reference.
Add SQL language reference.

mehant/incubator-calcite,joshelser/calcite-avatica,julianhyde/optiq,arina-ielchiieva/calcite,amansinha100/incubator-calcite,googleinterns/calcite,sudheeshkatkam/incubator-calcite,hsuanyi/incubator-calcite,googleinterns/calcite,hsuanyi/optiq,jinfengni/optiq,arina-ielchiieva/calcite,looker-open-source/calcite-avatica,joshelser/incubator-calcite,sudheeshkatkam/incubator-calcite,jcamachor/calcite,YrAuYong/incubator-calcite,dindin5258/calcite,yeongwei/incubator-calcite,amansinha100/incubator-calcite,apache/calcite-avatica,looker-open-source/calcite-avatica,xhoong/incubator-calcite,glimpseio/incubator-calcite,apache/calcite,yeongwei/incubator-calcite,googleinterns/calcite,vlsi/calcite,wanglan/calcite,sreev/incubator-calcite,wanglan/calcite,julianhyde/calcite,YrAuYong/incubator-calcite,vlsi/incubator-calcite,wanglan/calcite,datametica/calcite,minji-kim/calcite,datametica/calcite,YrAuYong/incubator-calcite,YrAuYong/incubator-calcite,looker-open-source/calcite-avatica,amoghmargoor/incubator-calcite,looker-open-source/calcite,b-slim/calcite,yeongwei/incubator-calcite,datametica/calcite,mapr/incubator-calcite,yeongwei/incubator-calcite,sreev/incubator-calcite,arina-ielchiieva/calcite,b-slim/calcite,looker-open-source/calcite,mprudhom/incubator-optiq,vlsi/calcite,sreev/incubator-calcite,dindin5258/calcite,looker-open-source/calcite,jinfengni/optiq,apache/calcite,sreev/incubator-calcite,sudheeshkatkam/incubator-calcite,julianhyde/optiq,b-slim/calcite,looker-open-source/calcite,b-slim/calcite,julianhyde/calcite,devth/calcite,mehant/incubator-calcite,apache/calcite,hsuanyi/incubator-calcite,minji-kim/calcite,glimpseio/incubator-calcite,apache/calcite,xhoong/incubator-calcite,datametica/calcite,apache/calcite-avatica,looker-open-source/calcite-avatica,jcamachor/calcite,minji-kim/calcite,jinfengni/incubator-optiq,julianhyde/calcite,jcamachor/calcite,adeshr/incubator-calcite,glimpseio/incubator-calcite,arina-ielchiieva/calcite,jcamachor/calcite,julianhyde/calcite,looker-open-source/calcite,amoghmargoor/incubator-calcite,mprudhom/incubator-optiq,hsuanyi/incubator-calcite,arina-ielchiieva/calcite,looker-open-source/calcite,apache/calcite,amoghmargoor/incubator-calcite,jinfengni/incubator-optiq,joshelser/calcite-avatica,googleinterns/calcite,googleinterns/calcite,joshelser/incubator-calcite,vlsi/calcite,joshelser/calcite-avatica,minji-kim/calcite,adeshr/incubator-calcite,adeshr/incubator-calcite,apache/calcite-avatica,vlsi/calcite,apache/calcite-avatica,googleinterns/calcite,sudheeshkatkam/incubator-calcite,amoghmargoor/incubator-calcite,hsuanyi/optiq,julianhyde/calcite,joshelser/incubator-calcite,devth/calcite,apache/calcite,hsuanyi/incubator-calcite,dindin5258/calcite,looker-open-source/calcite-avatica,xhoong/incubator-calcite,dindin5258/calcite,julianhyde/calcite,minji-kim/calcite,dindin5258/calcite,jcamachor/calcite,dindin5258/calcite,vlsi/calcite,wanglan/calcite,vlsi/incubator-calcite,mapr/incubator-calcite,datametica/calcite,apache/calcite-avatica,xhoong/incubator-calcite,glimpseio/incubator-calcite,jcamachor/calcite,datametica/calcite,adeshr/incubator-calcite,b-slim/calcite,joshelser/incubator-calcite,vlsi/calcite