postgresql使用filter進行多維度聚合
你有沒有碰到過有這樣一種場景，就是我們需要看一下某個時間段內各種維度的彙總，比如這樣：最近三年我們賣了多少貨？有多少訂單？平均交易價格多少？每個店鋪賣了多少？交易成功的訂單有多少？交易失敗的訂單有多少？ 等等...，假使這些數據的明細都在一個表內，該這麼做呢？ 有沒有簡單方式？還有如何減少全表掃描以更改的拿到數據?
如果只是簡單的利用聚合拿到數據可能您需要寫很多sql，具體表現爲每一個問題寫一段sql 相互之間join起來，這樣也許是個好主意，不過對於未充分優化的數據庫系統，針對每一塊的問題求解可能就是一個巨大的表掃描，當然還有一個問題就是重複的where條件，所以能不能把相同的where條件抽取出來以簡化sql呢？讓我們思考一下，也許有這樣的解決辦法~ （結論是有，當然有，哈哈哈~）
首先我提供下基本的表結構及測試數據
基本表結構
CREATE TABLE "order_info" (
"id" numeric(22) primary key ,
"oid" varchar(100) COLLATE "pg_catalog"."default", -- 訂單號
"shop" varchar(100) COLLATE "pg_catalog"."default", -- 店鋪
"date" date NOT NULL, --訂單日期
"status" varchar(100) COLLATE "pg_catalog"."default", -- 訂單狀態
"payment" numeric(18,2), -- 交易支付金額
"product" varchar(100) COLLATE "pg_catalog"."default" -- 產品名稱
);
初始化表數據
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217794', '16135476150276171', '店鋪2', '2019-07-01', '交易失敗', '139.00', '某某單品02');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217761', '16132502190562224', '店鋪2', '2020-05-01', '交易成功', '9.90', '某某禮盒');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217795', '16122384743927326', '店鋪3', '2019-06-01', '交易失敗', '357.00', '某某套裝');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217796', '16138945194036971', '店鋪2', '2019-05-01', '交易中', '59.90', '某某單品');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217797', '16131909251901209', '店鋪1', '2019-04-01', '交易失敗', '359.00', '某某贈品');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217798', '16135391935074761', '店鋪2', '2019-03-01', '交易失敗', '139.00', '某某單品01');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217762', '16132472268456370', '店鋪3', '2020-04-01', '交易成功', '79.00', '某某單品02');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217763', '16122960304700879', '店鋪2', '2020-03-01', '交易成功', '357.00', '某某單品03');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217764', '16139491271154103', '店鋪1', '2020-02-01', '交易成功', '139.00', '某某禮盒');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217765', '16122930818314343', '店鋪2', '2020-01-01', '交易成功', '79.00', '某某套裝');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217766', '12581133644786193', '店鋪3', '2019-12-01', '交易成功', '79.00', '某某單品06');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217767', '16122904539659361', '店鋪2', '2019-11-01', '交易成功', '359.00', '某某單品07');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217752', '16136227870425525', '店鋪1', '2021-02-01', '交易成功', '4.90', '某某單品08');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217753', '16139781339192958', '店鋪2', '2021-01-01', '交易失敗', '89.00', '某某禮盒');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217754', '16136217317281545', '店鋪3', '2020-12-01', '交易中', '6.90', '某某套裝');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217756', '16123091065663616', '店鋪1', '2020-10-01', '交易失敗', '95.00', '某某單品01');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217757', '16123013684517817', '店鋪2', '2020-09-01', '交易中', '79.00', '某某單品02');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217758', '16139678011781848', '店鋪3', '2020-08-01', '交易中', '59.90', '某某單品03');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217759', '16139576187535157', '店鋪2', '2020-07-01', '交易成功', '9.90', '某某單品04');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217791', '16132066938478413', '店鋪4', '2019-10-01', '交易成功', '359.00', '某某單品05');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217792', '12589185047405699', '店鋪5', '2019-09-01', '交易成功', '6.90', '某某單品06');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217760', '16139601047542860', '店鋪1', '2020-06-01', '交易成功', '359.00', '某某單品07');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217837', '16138184483906283', '店鋪4', '2021-03-04', '交易成功', '359.00', '某某單品02');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217838', '16134581997874325', '店鋪5', '2021-03-04', '交易成功', '299.00', '某某單品03');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217839', '16131099658443817', '店鋪3', '2021-03-04', '交易成功', '9.90', '某某單品04');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217840', '16131081649792689', '店鋪2', '2021-03-04', '交易成功', '15.89', '某某單品05');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217841', '16131087729266410', '店鋪1', '2021-03-04', '交易成功', '49.00', '某某禮盒');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217842', '16138126191679446', '店鋪2', '2021-03-04', '交易成功', '6.90', '某某套裝');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217843', '16138166422967430', '店鋪3', '2021-03-04', '交易成功', '579.00', '某某單品');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217844', '16121412752067761', '店鋪2', '2021-03-04', '交易成功', '359.00', '某某贈品');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217845', '12580980977280299', '店鋪3', '2021-03-04', '交易成功', '359.00', '某某單品01');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217799', '16135358470437562', '店鋪2', '2019-02-01', '交易成功', '339.00', '某某單品02');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217800', '16135320673129243', '店鋪1', '2019-01-01', '交易成功', '299.00', '某某單品03');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217801', '16131874317933316', '店鋪2', '2021-03-04', '交易失敗', '359.00', '某某禮盒');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217802', '16131792695743424', '店鋪3', '2021-03-04', '交易中', '79.00', '某某套裝');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217803', '16122278134767414', '店鋪2', '2021-03-04', '交易失敗', '99.00', '某某單品06');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217804', '16131790093817033', '店鋪3', '2021-03-04', '交易成功', '15.89', '某某單品03');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217805', '16135230297238674', '店鋪2', '2021-03-04', '交易成功', '247.81', '某某禮盒');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217806', '16135220588746073', '店鋪1', '2021-03-04', '交易成功', '25.79', '某某套裝');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217831', '16131159355051065', '店鋪3', '2021-03-04', '交易成功', '359.00', '某某單品07');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217832', '16131196017949185', '店鋪2', '2021-03-04', '交易成功', '4.90', '某某單品08');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217833', '16131207902538323', '店鋪1', '2021-03-04', '交易成功', '339.00', '某某禮盒');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217834', '12580998687179491', '店鋪2', '2021-03-04', '交易成功', '15.89', '某某套裝');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217835', '16138210374123403', '店鋪3', '2021-03-04', '交易成功', '189.00', '某某單品11');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217836', '16138242030068870', '店鋪2', '2021-03-04', '交易成功', '39.90', '某某單品01');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217846', '16134490408511254', '店鋪3', '2021-03-04', '交易成功', '238.00', '某某單品07');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217847', '16134370276544509', '店鋪2', '2021-03-04', '交易成功', '100.00', '某某單品08');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217854', '16121202131801564', '店鋪1', '2021-03-04', '交易成功', '359.00', '某某禮盒');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217855', '16121178732153257', '店鋪2', '2021-03-04', '交易成功', '499.00', '某某套裝');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217856', '16130716264223504', '店鋪3', '2021-03-04', '交易成功', '9.81', '某某單品11');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217857', '16130734211002184', '店鋪2', '2021-03-04', '交易成功', '9.90', '某某單品01');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217858', '16134100289526412', '店鋪5', '2021-03-04', '交易成功', '359.00', '某某單品02');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217859', '16134103486626066', '店鋪3', '2021-03-04', '交易成功', '189.00', '某某單品03');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217860', '16121142702989101', '店鋪2', '2021-03-04', '交易成功', '259.00', '某某單品04');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217861', '16137767910421049', '店鋪1', '2021-03-04', '交易成功', '299.00', '某某單品05');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217862', '16121018164688502', '店鋪5', '2021-03-04', '交易成功', '299.00', '某某單品06');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217887', '16120248152353139', '店鋪3', '2021-03-04', '交易成功', '9.90', '某某單品07');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217888', '16136951424489400', '店鋪2', '2021-06-07', '交易成功', '9.90', '某某單品08');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217889', '16136924750406856', '店鋪1', '2021-05-07', '交易成功', '6.90', '某某單品02');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217916', '16119522769335722', '店鋪2', '2021-02-07', '交易中', '6.90', '某某單品03');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217917', '12588728512745597', '店鋪1', '2021-01-07', '交易成功', '89.00', '某某禮盒');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217848', '16138039330168579', '店鋪2', '2021-03-04', '交易成功', '314.00', '某某套裝');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217849', '16130922810196821', '店鋪3', '2021-03-04', '交易失敗', '199.00', '某某單品06');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217890', '16136941319549862', '店鋪2', '2021-04-07', '交易成功', '79.00', '某某單品07');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217793', '16135470341712568', '店鋪1', '2019-08-01', '交易成功', '180.00', '某某單品08');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217755', '16132741910343927', '店鋪2', '2020-11-01', '交易成功', '6.90', '某某單品11');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217807', '16138852921447547', '店鋪2', '2021-03-04', '交易成功', '238.00', '某某單品06');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217891', '16133225738639350', '店鋪1', '2021-03-07', '交易失敗', '49.00', '某某單品08');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217850', '12591040185524596', '店鋪2', '2021-03-04', '交易中', '6.90', '某某禮盒');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217851', '16130856267945884', '店鋪3', '2021-03-04', '交易成功', '299.00', '某某套裝');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217852', '16121205784010168', '店鋪2', '2021-03-04', '交易失敗', '19.70', '某某單品11');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217853', '16137863356208213', '店鋪1', '2021-03-04', '交易中', '19.70', '某某單品01');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217958', '12588659047949994', '店鋪2', '2019-08-07', '交易成功', '9.90', '某某單品11');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217959', '16117515001200723', '店鋪3', '2019-07-07', '交易成功', '99.00', '某某單品01');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217960', '16126968285988680', '店鋪2', '2019-06-07', '交易成功', '6.90', '某某單品02');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217985', '12588376827205292', '店鋪3', '2019-05-07', '交易成功', '337.00', '某某單品03');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217986', '12588344485529392', '店鋪2', '2019-04-07', '交易成功', '139.00', '某某單品04');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217987', '16125503474522303', '店鋪1', '2021-03-04', '交易失敗', '9.81', '某某單品05');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217988', '16129065212801070', '店鋪2', '2021-03-04', '交易中', '359.00', '某某禮盒');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217989', '16125466354777343', '店鋪3', '2021-03-04', '交易中', '49.00', '某某套裝');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217918', '16136147162483080', '店鋪2', '2020-12-07', '交易成功', '6.90', '某某單品02');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217919', '12580777996543594', '店鋪3', '2020-11-07', '交易成功', '299.00', '某某單品03');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217926', '16135916055519587', '店鋪2', '2020-04-07', '交易成功', '359.00', '某某單品04');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217927', '16128748461350415', '店鋪3', '2020-03-07', '交易成功', '9.90', '某某單品05');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217952', '16130772755076508', '店鋪2', '2020-02-07', '交易成功', '139.00', '某某單品06');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217953', '16130750443205377', '店鋪4', '2020-01-07', '交易成功', '4.90', '某某單品07');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217954', '16117587731623017', '店鋪5', '2019-12-07', '交易成功', '4.90', '某某單品08');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217955', '16127065063959102', '店鋪3', '2019-11-07', '交易成功', '69.00', '某某單品02');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217920', '16128970251579383', '店鋪2', '2020-10-07', '交易成功', '90.00', '某某單品03');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217921', '16128964832564531', '店鋪2', '2020-09-07', '交易成功', '175.00', '某某禮盒');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217922', '16135999993916188', '店鋪3', '2020-08-07', '交易成功', '139.00', '某某套裝');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217923', '16136051439214988', '店鋪2', '2020-07-07', '交易成功', '9.90', '某某單品06');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217924', '16119347018161682', '店鋪5', '2020-06-07', '交易成功', '9.90', '某某單品07');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217925', '16132344851576556', '店鋪3', '2020-05-07', '交易成功', '9.90', '某某單品08');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217956', '16130631650814848', '店鋪2', '2019-10-07', '交易成功', '79.00', '某某禮盒');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217957', '16130549587928221', '店鋪1', '2019-09-07', '交易成功', '6.90', '某某套裝');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217990', '12590493961403993', '店鋪2', '2021-03-04', '交易成功', '129.00', '某某單品');
INSERT INTO "order_info"("id", "oid", "shop", "date", "status", "payment", "product") VALUES ('051802588006217991', '16115933800269974', '店鋪1', '2021-03-04', '交易成功', '79.00', '某某贈品');
準備個問題
這裏我找幾個基本的問題，比如： 1.我們要找最近兩年（2019、2020）有多少筆交易？+ 2.交易成功的平均價格多少？ + 3.交易成功的訂單有多少？ + 4.店鋪1、2、3分別賣了多少？
使用filter前
對於以上同類多維度數據求解這裏推薦filter,可能熟悉同學大概會記得有這麼個用法，不過我們還是簡單的思考下：
如果我們將條件篩選放在一個查詢裏面(不含子查詢及表連接) , 這樣會在末尾where條件內放置公共條件, 隨後我們使用filter對每個結果進行特定的篩選，也許就好了
OK，來嘗試使用filter解決以下問題： 找最近兩年（2019、2020）有多少筆交易？
問題求解
我們上面拋出了個問題： 找最近兩年（2019、2020）有多少筆交易？
很顯然這個結果集框定的範圍是2019年和2020年 ，所以~
select
count(1) as 交易總訂單_20_and_19,
count(1) filter ( where date>=to_date('2020-01-01','yyyy-MM-dd') and date < to_date('2021-01-01','yyyy-MM-dd') ) as 交易總訂單_20,
count(1) filter ( where date>=to_date('2019-01-01','yyyy-MM-dd') and date < to_date('2020-01-01','yyyy-MM-dd') ) as 交易總訂單_19
from order_info
where date >= date_trunc('year',to_date('2021-07-12','yyyy-MM-dd')+interval '-2 year')::date
and date < date_trunc('year',to_date('2021-07-12','yyyy-MM-dd'))::date
運行結果：
交易總訂單_20_and_19 | 交易總訂單_20 | 交易總訂單_19
----------------------+---------------+---------------
45 | 24 | 21
(1 row)
如果你是首次使用filter子句，這裏我簡單的驗證下，就驗證2019年多少訂單吧：
select count(1) as 交易總訂單_19 from order_info where date>=to_date('2019-01-01','yyyy-MM-dd') and date < to_date('2020-01-01','yyyy-MM-dd') ;
交易總訂單_19
---------------
21
(1 row)
【注意，不論您篩選的上面什麼範圍內的數據，一定要考慮 where條件一定要框定當前所有結果集合最大的範圍，不然sql運行的結果不及預計~ 】
最後，對於一開始的問題給出一個參考sql：
select
count(1) as 交易總訂單_20_and_19,
count(1) filter ( where date>=to_date('2020-01-01','yyyy-MM-dd') and date < to_date('2021-01-01','yyyy-MM-dd') ) as 交易總訂單_20,
count(1) filter ( where date>=to_date('2019-01-01','yyyy-MM-dd') and date < to_date('2020-01-01','yyyy-MM-dd') ) as 交易總訂單_19,
avg(payment) filter (where status='交易成功' ) as 交易成功的均價,
count(1) filter (where status='交易成功' ) as 交易成功的訂單數,
count(1) filter (where status!='交易成功' ) as 交易失敗的訂單數,
sum(payment) filter (where status='交易成功' and shop='店鋪1' ) as 店鋪1交易額,
sum(payment) filter (where status='交易成功' and shop='店鋪2' ) as 店鋪2交易額,
sum(payment) filter (where status='交易成功' and shop='店鋪3' ) as 店鋪3交易額
from order_info
where date >= date_trunc('year',to_date('2021-07-12','yyyy-MM-dd')+interval '-2 year')::date
and date < date_trunc('year',to_date('2021-07-12','yyyy-MM-dd'))::date