① oracle sql查詢時提示 用戶數據中的connect by 循環 報錯是什麼原因
一般是數據錯誤導致了死循環。
如數據為這樣：
ID 父ID 值
1 2 10
2 1 20
如圖，ID為1的父ID為2，而同時ID為2的父ID是1，這樣的話，就會互相認對方的ID為父ID，就會造成一個死循環，這種錯誤，一般不用修改語句，需要正確檢查數據的正確性。
② oracle動態執行sql語句報錯請各位大蝦幫忙看一下哪裡出錯了！
你的這句sql有些問題。你這里的count('username') 幹嘛要加引號啊？
DECLARE
sql_string VARCHAR2(100);
BEGIN
sql_string := 'select count(username) from sys.user_users' ;
dbms_output.put_line( sql_string);
EXECUTE IMMEDIATE sql_string;
END;
這樣就可以了。
如果你的username是想動態的反映當前的登錄用戶的話要改成user。如下：
DECLARE
sql_string VARCHAR2(100);
BEGIN
sql_string := 'select count('||user||') from sys.user_users' ;
dbms_output.put_line( sql_string);
EXECUTE IMMEDIATE sql_string;
END;
但是也不能執行成功因為user_users' 裡面不一定有這個列。
③ oracle資料庫動態SQL語句問題
是這樣子的：
正常的SQL應該是這樣：
SELECT COUNT(*) FROM USER_TABLES WHERE TABLE_NAME='EMP';
然後V_SQL:='';最外層也是有引號的
當表名是變數，但是我們查的時候是需要加上單引號的，如果最外面的單引號的話，則裡面的單引號就需要單引號再加單引號這樣來引用的。
所以，如果你測試你的V_SQL寫的正常不正常的話，可以用raise_application_error(-20201,V_SQL);查看，因為這樣輸出的是正常的sql的哦。
④ java操作資料庫Oracle 當出現SQL異常時用e.getMessage()獲取異常信息，為什麼在異常信息末尾有個換行符
Interactive PlottingExample — Selecting Plotting Points from the Screen
You can interact with graphs or generate x-y coordinates interactively. The ginput function enables you to use the mouse or the arrow keys to select points to plot. ginput returns the coordinates of the pointer's position, either the current position or the position when a mouse button or key is pressed. For more information see the ginput function. You can use it to pick points on a graph to return their x and y values for processing, to outline an area of interest, or to draw arbitrary shapes.
This example illustrates the use of ginput with the spline function to create a curve by interpolating in two dimensions.
First, select a sequence of points, [x,y], in the plane with ginput. Then pass two one-dimensional splines through the points, evaluating them with a spacing one-tenth of the original spacing:
axis([0 10 0 10])hold on% Initially, the list of points is empty.xy = [];n = 0;% Loop, picking up the points.disp('Left mouse button picks points.')disp('Right mouse button picks last point.')but = 1;while but == 1 [xi,yi,but] = ginput(1); plot(xi,yi,'ro') n = n+1; xy(:,n) = [xi;yi];end% Interpolate with a spline curve and finer spacing.t = 1:n;ts = 1: 0.1: n;xys = spline(t,xy,ts);
% Plot the interpolated curve.plot(xys(1,:),xys(2,:),'b-');hold off
This plot shows some typical output: