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PG库常用函数记录计算质心点坐标：ST_X(ST_Centroid(geom)) ST_Y(ST_Centroid(geom))计算图斑面积：ST_Area(geom)计算周长：ST_Perimeter(geom)计算长度：ST_Length(geom)计算最大最小 X Y:ST_XMin ST_YMin ST_XMax ST_YMax截取字符串：substring(zldwdm,1,6)PG库 查询某张表字段类型及字段名称：SELECT column_name,udt_na

Sqlite3查询数据库的总表数：select name from sqlite_master where type='table' order by name获取某张表的所有字段信息：PRAGMA table_info("TableName")TableName为待查询表名查询一张表有多少条数据select count(*) from TableNamePostgresql对数据表查询指令：查询指定表的字段名及类型：selecta.attname as fiel.