postgresql學(xué)習(xí)手冊：sql語言函數(shù)(編輯修改稿)
2024-10-19 10:29 本頁面
【文章內(nèi)容簡介】 e stockid= str(nid)stockname = 39。str_name39。stockname like 39。% find this %39。stockname like 39。[azAZ]%39。([]指定值的范圍)stockname like 39。[^FM]%39。(^排除指定范圍)只能在使用like關(guān)鍵字的where子句中使用通配符)or stockpath = 39。stock_path39。or stocknumber 1000and stockindex = 24not stocksex = 39。man39。stocknumber between 20 and 100stocknumber in(10,20,30)order by stockid desc(asc)排序，desc降序，asc升序order by 1,2by列號(hào)stockname =(select stockname from stock_informationwhere stockid= 4)子查詢除非能確保內(nèi)層select只返回一個(gè)行的值，否則應(yīng)在外層where子句中用一個(gè)in限定符select distinct column_name form table_namedistinct指定檢索獨(dú)有的列值，不重復(fù)select stocknumber ,“stocknumber + 10” = stocknumber + 10 from table_nameselect stockname , “stocknumber” = count(*)from table_name group by stocknamegroup by 將表按行分組,指定列中有相同的值having count(*)= 2having選定指定的組select *from table1, table2where *= ， =* select stockname from table1union [all]union合并查詢結(jié)果集，all保留重復(fù)行select stockname from table2***insert***insert into table_name(Stock_name,Stock_number)value(“xxx”,“xxxx”)value(select Stockname , Stocknumber from Stock_table2)value為select語句***update***update table_name set Stockname = “xxx” [where Stockid = 3]Stockname = defaultStockname = nullStocknumber = Stockname + 4***delete***delete from table_name where Stockid = 3truncate table_name刪除表中所有行，仍保持表的完整性drop table table_name完全刪除表***alter table***修改數(shù)據(jù)庫表結(jié)構(gòu)alter table add column_name char(2)null.....sp_help table_name顯示表已有特征create table table_name(name char(20), age smallint, lname varchar(30))insert into table_name select.........實(shí)現(xiàn)刪除列的方法（創(chuàng)建新表）alter table table_name drop constraint Stockname_default刪除Stockname的default約束***function(/*常用函數(shù)*/)***統(tǒng)計(jì)函數(shù)AVG求平均值COUNT統(tǒng)計(jì)數(shù)目MAX求最大值MIN求最小值SUM求和AVGuse panguselect avg(e_wage)as dept_avgWagefrom employeegroup by dept_idMAX求工資最高的員工姓名use panguselect e_namefrom employeewhere e_wage =(select max(e_wage)from employee)STDEV()STDEV()函數(shù)返回表達(dá)式中所有數(shù)據(jù)的標(biāo)準(zhǔn)差STDEVP()STDEVP()函數(shù)返回總體標(biāo)準(zhǔn)差VAR()VAR()函數(shù)返回表達(dá)式中所有值的統(tǒng)計(jì)變異數(shù)VARP()VARP()函數(shù)返回總體變異數(shù)算術(shù)函數(shù)/***三角函數(shù)***/SIN(float_expression)返回以弧度表示的角的正弦COS(float_expression)返回以弧度表示的角的余弦TAN(float_expression)返回以弧度表示的角的正切COT(float_expression)返回以弧度表示的角的余切/***反三角函數(shù)***/ASIN(float_expression)返回正弦是FLOAT 值的以弧度表示的角ACOS(float_expression)返回余弦是FLOAT 值的以弧度表示的角ATAN(float_expression)返回正切是FLOAT 值的以弧度表示的角ATAN2(float_expression1,float_expression2)返回正切是float_expression1 /float_expression2的以弧度表示的角DEGREES(numeric_expression)把弧度轉(zhuǎn)換為角度返回與表達(dá)式相同的數(shù)據(jù)類型可為INTEGER/MONEY/REAL/FLOAT 類型RADIANS(numeric_expression)把角度轉(zhuǎn)換為弧度返回與表達(dá)式相同的數(shù)據(jù)類型可為INTEGER/MONEY/REAL/FLOAT 類型EXP(float_expression)返回表達(dá)式的指數(shù)值LOG(float_expression)返回表達(dá)式的自然對(duì)數(shù)值LOG10(float_expression)返回表達(dá)式的以10 為底的對(duì)數(shù)值SQRT(float_expression)返回表達(dá)式的平方根/***取近似值函數(shù)***/CEILIN
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