CURSOR <游标名称> IS <游标名称>%ROWTYPE; BEGIN OPEN <游标名称> LOOP FETCH <游标名称> INTO ; EXIT WHEN <游标名称>%NOTFOUND; <其它要执行的代码> END LOOP; CLOSE <游标名称>; END <存储过程名称>; / 代码例子: 复制内容到剪贴板 程序代码 TRUNCATE TABLE loop_test; DECLARE CURSOR ao_cur IS ...
cursor 这货是游标 is select * from 去年买了个表 where name = ‘祖安少年’; 联盟新手 去年买了个表%rowType; --从游标里取出来的值放在这里。 打开游标 open 这货是游标; 读取数据 fetch 这货是游标 into 联盟新手; 关闭游标 close 这货是游标; 游标&loop 联合公演 open 这货是游标; 我是游标儿子...
Once a cursor has been opened, it can be manipulated with the statements described here. These manipulations need not occur in the same function that opened the cursor to begin with. You can return a refcursor value out of a function and let the caller operate on the cursor. 3.1. FETCH F...
Once a cursor has been opened, it can be manipulated with the statements described here. These manipulations need not occur in the same function that opened the cursor to begin with. You can return a refcursor value out of a function and let the caller operate on the cursor. 3.1. FETCH F...
游标(Cursor)是一种数据库编程机制,用于处理查询结果集。它并非直接返回全部查询结果,而是作为一个可控制的指针,允许程序员逐行访问、操作或提取数据。游标的核心价值体现在以下几个方面: 内存优化:对于大数据量查询,游标仅需一次性加载少量数据到内存,避免一次性加载整个结果集导致的内存溢出。
FETCH FROM c3 INTO rowvar; EXIT WHEN NOT FOUND; END LOOP; CLOSE c3; END$$; Example of MOVE a cursor without fetching data MOVErepositions a cursor without retrieving any data and works such as theFETCHcommand, except it only repositions the cursor in the dataset and ...
cursor.execute和 SQL SELECT 语句来读取数据。 cursor.fetchall(),以接受查询并返回要循环访问的结果集。 Python # Fetch all rows from tablecursor.execute("SELECT * FROM pharmacy;") rows = cursor.fetchall()# Print all rowsforrowinrows: print("Data row = (%s, %s)"%(str(row[0]), str(row...
BEGIN; SELECT * FROM myfunc('a', 'b'); FETCH ALL FROM a; FETCH ALL FROM b; COMMIT; for游标循环 [ <> ] FOR recordvar IN bound_cursorvar [ ( [ argument_name := ] argument_value [, ...] ) ] LOOP statements END LOOP [ label ]; 异常消息处理 抛出异常 RAISE [ level ] ...
Under the covers, the library calls the PostgreSQL cursor operations with the pseudo-code: SET cursor_tuple_fraction TO 1.0; DECLARE cursor_1 CURSOR WITH HOLD FOR select * from widgets; loop rows = FETCH 100 FROM cursor_1; rows.each {|row| yield row} until rows.size < 100; CLOSE curso...
A FETCH statement sets FOUND true if it returns a row, false if no row is returned. A MOVE statement sets FOUND true if it successfully repositions the cursor, false otherwise. A FOR or FOREACH statement sets FOUND true if it iterates one or more times, else false. FOUND is set this...