if(OBJECT_ID('trigger_student_Insert','TR')is not null) --is not null print 'trigger_student_Insert 触发器已经存在' 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. --新增表 IF NOT EXISTS ( SELECT * FROM sysobjects WHERE id = object_id('DICT_CONFLICTRULECONFIG') AND...
Duplicate data in table I read some answered questions but they don't help me! This is my table: I want prevent duplicate data if their student_id and les_id were equal. How can I do it, I don't have much info about triggers......
the MySQL optimizer considers many techniques to efficiently performthe lookups involved in an SQL query. A query on a huge table can be performedwithout reading all the rows; a join involving several tables can be performedwithout comparing every combination of rows. The set of operations...
unique_subquery是一个索引查找函数,可以完全替换子查询,效率更高。 该类型替换了下面形式的IN子查询的ref: value IN (SELECT primary_key FROM single_table WHERE some_expr) 此处按照官网的格式未测试出例子来,若有例子的请留言,我测试更新 9、index_subquery 该联接类型类似于unique_subquery。可以替换IN子查询,...
*/ delimiter $$ # 将mysql默认的结束符由;换成$$ create trigger tri_after_insert_cmd after insert on cmd for each row begin # 表示SQL语句开始 if NEW.success = 'no' then # 新记录都会被MySQL封装成NEW对象insert into errlog(err_cmd,err_time) values(NEW.cmd,NEW.sub_time); end if; #...
ExplainCloseGroup("Trigger", NULL, true, es); }}/* Compute elapsed time in seconds since given timestamp */static doubleelapsed_time(instr_time *starttime){ instr_time endtime; INSTR_TIME_SET_CURRENT(endtime); INSTR_TIME_SUBTRACT(endtime, *starttime); return INSTR_TIME_GET_DOUBLE(endtim...
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We hope that this EDUCBA information on “EXPLAIN ANALYZE in PostgreSQL” was beneficial to you. You can view EDUCBA’s recommended articles for more information. Indexes in PostgreSQL GROUP BY PostgreSQL PostgreSQL Triggers PostgreSQL Operators
Init gangs cost: the duration that is taken to preprocess the execution plan that is generated by the QO and send the query request to the QE to trigger the start query phase. Unit: milliseconds. Start query cost: the duration of the initialization phase, which starts when the Init gangs...
the output column list for each node in the plan tree the schema-qualified table and function names the variables names in expressions together with the table alias the name of each trigger for which statistics are displayed COSTS Includes the estimated start-up cost, and total cost, plus the...