DECLARE 游标名 CURSOR FOR SELECT语句 #定义游标 OPEN 游标名 FETCH …(游标名) INTO … #遍历游标取出数据 CLOSE 游标名 PS:一个BGEIN END只能声明一个游标,打开的游标需进行关闭 ③预编译(可将字符串预编译为sql语句) PREPARE 语句名(不需要定义) FROM 字符串变量名 EXECUTE 语句名 每次执行完,需执行DEALL...
EXPLAIN SELECT SQL_NO_CACHE * FROM student WHERE student.age=30 AND student.name = 'abcd'; 可以使用idx_age,但是不能使用idx_age_classid_name。 EXPLAIN SELECT SQL_NO_CACHE * FROM student WHERE student.classId=1 AND student.name = 'abcd'; 完全没有使用上索引。 举例2: EXPLAIN SELECT SQL_...
for test in ( /*业务SQL(sql后面不需要加";")*/ select * from t) loop null; end loop; for x in (select p.plan_table_output from table(dbms_xplan.display_cursor(null, null, 'advanced -bytes -PROJECTION allstats last')) p) loop dbms_output.put_line(x.plan_table_output); end loop...
CREATE PROCEDURE explain_query_for_all_schemas(IN query VARCHAR(1000)) BEGIN DECLARE done BOOLEAN DEFAULT FALSE; DECLARE schema_name VARCHAR(64); DECLARE cur_schema_names CURSOR FOR SELECT schema_name_table.schema_name FROM schema_name_table; DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TR...
1991, yyyy Licensed Material - Program Property of IBM IBM Db2 Database SQL and XQUERY Explain Tool *** DYNAMIC *** === STATEMENT === Isolation Level = Cursor Stability Blocking = Block Unambiguous Cursors Query Optimization Class = 5 Partition Parallel = No Intra-Partition Parallel = No...
在早期版本的MongoDB中,cursor.explain() 返回了详细索引的子句数组。 Sort 阶段 如果MongoDB可以使用索引扫描来获取请求的排序顺序,则结果将不包括SORT阶段。 否则,如果MongoDB无法使用索引进行排序,则解释结果将包括SORT阶段。 在MongoDB 3.0之前,cursor.explain() 返回scanAndOrder字段以指定MongoDB是否可以使用索引顺...
Cursor Stability Blocking = Block Unambiguous Cursors Query Optimization Class = 5 Partition Parallel = No Intra-Partition Parallel = No SQL Path = "SYSIBM", "SYSFUN", "SYSPROC", "SYSIBMADM", "SDINIRO" Statement: SELECT e.lastname, e.job, d.deptname, d.location, p.projname FROM ...
LANGUAGE SQL BEGIN DECLARE v_city char(20); DECLARE v_count int; SET v_message = ''; select count(*) into v_count from test; BEGIN DECLARE v_CUR CURSOR FOR SELECT city FROM test FOR READ ONLY; OPEN v_CUR; WHILE v_count > 0 DO ...
The SQL Explain Plan option generates an explain plan for a query. To generate an explain plan, either highlight a query, or if nothing is highlighted and the language type is SQL mode, separate the queries in the editor by semi-colons and position the cursor within the query to explain,...
This prevents problems in * the case that the EXPLAIN is in a portal or plpgsql function and is * executed repeatedly. (See also the same hack in DECLARE CURSOR and * PREPARE.) XXX FIXME someday. */ rewritten = QueryRewrite(castNode(Query, copyObject(stmt->query))); /* emit opening...