CREATE TABLE department(   ID INT PRIMARY KEY                         NOT NULL,   d_code                                     VARCHAR(50),   d_name                                     VARCHAR(50)     NOT NULL,   d_parentID                                 INT             NOT NULL  DEFAULT 0); --insert into department values(1,‘001‘,‘office‘);--insert into department values(2,‘002‘,‘office‘,1);

drop function f_getNewID(text,text);create or replace function f_getNewID(myTableName text,myFeildName text) returns integer as $$declare    mysql text;        myID integer;begin    mysql:=‘select max( $1 ) from $2‘;        execute mysql into myID using myFeildName,myTableName;         if myID is null or myID=0 then return 1;    else return myID+1;      end if;end;$$ language plpgsql;

--大家可以试一下，上面这个是会报错的
--select f_getNewID(‘department‘,‘ID‘);
--出错！

EXECUTE ‘SELECT count(*) FROM mytable WHERE inserted_by = $1 AND inserted <= $2‘   INTO c   USING checked_user, checked_date;

--这个看了？---------------------------------------EXECUTE ‘SELECT count(*) FROM ‘    || quote_ident(tabname)    || ‘ WHERE inserted_by = $1 AND inserted <= $2‘   INTO c   USING checked_user, checked_date;--这个看了？---------------------------------------EXECUTE ‘UPDATE tbl SET ‘        || quote_ident(colname)        || ‘ = ‘        || quote_literal(newvalue)        || ‘ WHERE key = ‘        || quote_literal(keyvalue);--=============================--好吧， 我改------------------------------------------------------drop function f_getNewID(text,text);create or replace function f_getNewID(myTableName text,myFeildName text) returns integer as $$declare    mysql text;    myID integer;begin    mysql:=‘select max(‘        || quote_ident(myFeildName)         ||‘) from ‘        || quote_ident(myTableName);    execute mysql into myID;     --using myTableName,myFeildName;        if myID is null or myID=0 then return 1;    else return myID+1;      end if;end;$$ language plpgsql;--==============================--漂亮，成功了！
--But Why?
--注意 对象（表名、字段名等）是不可以直接用变量的，要用  quote_ident()
-------------------------------------------------------postgres=# select f_getnewid(‘department‘,‘ID‘);--错误:  字段 "ID" 不存在--第1行select max("ID") from department                ^--查询:  select max("ID") from department--背景:  在EXECUTE的第10行的PL/pgSQL函数f_getnewid(text,text)--===============================--什么情况，ID怎么会有双引号，引号，号，号？？？------------------------------------------------------------这里要感谢大神：权宗亮@飞象数据
--改成这样：

postgres=# select f_getnewid(‘department‘,‘id‘); f_getnewid------------          2(1 行记录)

----终于成功了！大小写还有区别吗？？？ --but why? --当在命令行输入

CREATE TABLE role(   ID                                         INT PRIMARY KEY NOT NULL,   r_name                                     VARCHAR(50)     NOT NULL,   r_paretnID                                 INT             NOT NULL    DEFAULT 0  );

--结果在pgAdmin里看到的却是小写的

--同样，如果是在QUERY TOOLS 下用这样的语句创建还是 所有的字体名为小写
--如果我就想大写怎么办？？？？
--要这样写

CREATE TABLE "RoleUPER"(   "ID"                                         INT PRIMARY KEY NOT NULL,   r_name                                     VARCHAR(50)     NOT NULL,   "r_paretnID"                                 INT             NOT NULL    DEFAULT 0  );

--再用大象看看

--可以了！ 

create or replace function f_getNewID(myTableName text,myFeildName text) returns integer as $$declare    mysql text;        myID integer;begin    mysql:=‘select max(‘|| $2 || ‘ ) from ‘||$1;        execute mysql into myID using myFeildName,myTableName;     if myID is null or myID=0 then return 1;    else return myID+1;      end if;end;$$ language plpgsql;