一、在使用 date_format、from_unixtime、to_days、yearweek 函数时，Gbase 8s 数据库不支持，可以使用创建 UDR 外部函数来实现
二、登录命令控制台或者使用 navicat 连接 Gbase 数据库
这里使用 navicat ，点击新增连接选择 PostGreSql 驱动，添加地址、账号、密码
连接数据库后，选中目标库选中目标模式，再点击函数-新增函数执行以下语句即可
注意：这里 选中 public 模式，使用 mss 用户，自行修改函数中对应的内容（ 例如：FUNCTION “public”.“date_format”、OWNER TO “mss”）
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date_format 函数
CREATE OR REPLACE FUNCTION "public"."date_format"("ctimestamp" timestamptz, "informate" varchar)RETURNS "pg_catalog"."varchar" AS $BODY$-- Routine body goes here...DECLARE result_current_date varchar;BEGIN -- IF upper($1) = upper('YYYY-MM-DD') || upper($1) = upper('%Y-%M-%D') THEN -- SELECT to_char(now(),'YYYY-MM-DD') into result_current_date; -- END IF; -- -- -- IF upper($1) = upper('%Y-%M-%D %h:%m') || upper($1) = upper('%Y-%M-%D %h:%m') THEN -- SELECT to_char(now(),'YYYY-MM-DD HH:mm') into result_current_date; -- END IF; -- -- IF upper($1) = upper('%Y-%M-%D %h:%m:%s') || upper($1) = upper('%Y-%M-%D %h:%m:%s') THEN -- SELECT to_char(now(),'YYYY-MM-DD HH:mm:ss') into result_current_date; -- END IF;case upper($2)when upper('%Y') thenSELECT to_char(smalldatetime_to_timestamp($1),'YYYY') into result_current_date;when upper('%Y-%M') thenSELECT to_char(smalldatetime_to_timestamp($1),'YYYY-MM') into result_current_date; when upper('%Y-%M-%D') thenSELECT to_char(smalldatetime_to_timestamp($1),'YYYY-MM-DD') into result_current_date;when upper('%Y-%M-%D %h') thenSELECT to_char(smalldatetime_to_timestamp($1),'YYYY-MM-DD HH24') into result_current_date;when upper('%Y-%M-%D %h:%m') thenSELECT to_char(smalldatetime_to_timestamp($1),'YYYY-MM-DD HH24:MI') into result_current_date;when upper('%Y-%M-%D %h:%m:%s') thenSELECT to_char(smalldatetime_to_timestamp($1),'YYYY-MM-DD HH24:MI:ss') into result_current_date; when upper('%M') thenSELECT to_char(smalldatetime_to_timestamp($1),'MM') into result_current_date; when upper('%M-%D') thenSELECT to_char(smalldatetime_to_timestamp($1),'MM-DD') into result_current_date;when upper('%D') thenSELECT to_char(smalldatetime_to_timestamp($1),'DD') into result_current_date;when upper('%h') thenSELECT to_char(smalldatetime_to_timestamp($1),'HH24') into result_current_date; when upper('%h:%m') thenSELECT to_char(smalldatetime_to_timestamp($1),'HH24:MI') into result_current_date; when upper('%m') thenSELECT to_char(smalldatetime_to_timestamp($1),'MI') into result_current_date; when upper('%m:%s') thenSELECT to_char(smalldatetime_to_timestamp($1),'MI:ss') into result_current_date; when upper('%s') thenSELECT to_char(smalldatetime_to_timestamp($1),'ss') into result_current_date; when upper('%h:%m:%s') thenSELECT to_char(smalldatetime_to_timestamp($1),'HH24:MI:ss') into result_current_date; elseSELECT to_char(smalldatetime_to_timestamp($1),informate) into result_current_date;end case;RETURN result_current_date; END$BODY$LANGUAGE plpgsql VOLATILECOST 100;ALTER FUNCTION "public"."date_format"("ctimestamp" timestamptz, "informate" varchar) OWNER TO "mss";查询语句：
SELECT date_format(now(),'%Y-%M-%D %h:%m:%s'); -
from_unixtime 函数
CREATE OR REPLACE FUNCTION "public"."from_unixtime"("t" int8)RETURNS "pg_catalog"."timestamp" AS $BODY$DECLARE result_current_date timestamp;BEGIN select TO_TIMESTAMP(t) into result_current_date;RETURN result_current_date; END; $BODY$LANGUAGE plpgsql VOLATILECOST 100;ALTER FUNCTION "public"."from_unixtime"("t" int8) OWNER TO "mss";查询语句：
select from_unixtime(1692328679); -
to_days 函数
-- 参数 varchar类型 CREATE OR REPLACE FUNCTION "public"."to_days"("ctimestamp" varchar)RETURNS "pg_catalog"."int4" AS $BODY$-- Routine body goes here...DECLARE result_current_date int4;BEGINSELECT TIMESTAMPDIFF(day, '0001-01-01', $1) into result_current_date;RETURN result_current_date; END$BODY$LANGUAGE plpgsql VOLATILECOST 100;ALTER FUNCTION "public"."to_days"("ctimestamp" varchar) OWNER TO "mss";-- 参数 timestamptz 类型 CREATE OR REPLACE FUNCTION "public"."to_days"("ctimestamp" timestamptz)RETURNS "pg_catalog"."int4" AS $BODY$-- Routine body goes here...DECLARE result_current_date int4;BEGINSELECT TIMESTAMPDIFF(day, '0001-01-01', $1) into result_current_date;RETURN result_current_date; END$BODY$LANGUAGE plpgsql VOLATILECOST 100;ALTER FUNCTION "public"."to_days"("ctimestamp" timestamptz) OWNER TO "mss";查询语句：
select to_days(now()); -
yearweek 函数
CREATE OR REPLACE FUNCTION "public"."yearweek"("ctimestamp" timestamptz)RETURNS "pg_catalog"."int4" AS $BODY$-- Routine body goes here...DECLARE week_n int4;year_n int4;BEGINSELECT to_char(smalldatetime_to_timestamp($1),'YYYY') into year_n;SELECT trunc(1 + (smalldatetime_to_timestamp($1) - TRUNC(smalldatetime_to_timestamp($1), 'YEAR')) / 7) into week_n;RETURN ((year_n*100)+week_n); END$BODY$LANGUAGE plpgsql VOLATILECOST 100;ALTER FUNCTION "public"."yearweek"("ctimestamp" timestamptz) OWNER TO "mss";查询语句：
select YEARWEEK(now()); select YEARWEEK('2023-01-03 12');
