SELECT column_name FROM table_name WHERE column_name NOT IN (SELECT column_name FROM another_table) 注意,"NOT IN"操作符在使用时需要确保子查询的结果集不包含NULL值,否则可能导致不符合预期的结果。 "NOT EXISTS": "NOT EXISTS"操作符用于判断子查询的结果集是否为空,如果为空,则返回真(True)。它通...
Finding Records in One table that Don't Exist in Another Table (the Not-In Query) Now assume that we ONLY want to find the customers who have not placed any orders. Just like in the first scenario, we will use a Left Outer Join to accomplish this. This time, however, we’ll add ...
SQL Server performs sort, intersect, union, and difference operations using in-memory sorting and h...
assignment[, assignment]...INSERTinserts new rowsintoan existingtable. TheINSERT...VALUESandINSERT...SETformsofthe statementinsertrows basedonexplicitly specifiedvalues. TheINSERT...SELECTform inserts rows selectedfromanothertableortables.INSERTwithanONDUPLICATEKEYUPDATEclause enables existing rowstobe update...
How we work with data is also immensely important — if our database is optimized well (check one of our previous articles for advice on how to do that), we should not have that manyINorNOT INclauses to begin with. Even if we do, our SQL client of choice is usually capable of ass...
DELIMITER // CREATE PROCEDURE my_procedure (IN param1 INT, OUT result INT) BEGIN -- 存储过程的SQL语句SELECT column1 INTO result FROM my_table WHERE another_column = param1; END // DELIMITER ; 在上述示例中: my_procedure 是存储过程的名称。 (IN param1 INT, OUT result INT) 定义了输入参数...
5. UsingNOTEXISTS Clause Just as it sounds,theNOT EXISTSclause in SQL enables us to confirm the absence of related rows in anothertablebefore executing actions like deleting. Moreover, another standout benefit of using the NOT EXISTS clause is the scalability it offers. This comes into play ...
ON mytable.Id = another_table.Id (想象一下刚才讲的主键连接,两个相同的连成1条) WHERE condition(s) ORDER BY column, … ASC/DESC LIMIT num_limit OFFSET num_offset; 通过ON条件描述的关联关系;INNER JOIN 先将两个表数据连接到一起. 两个表中如果通过Id互相找不到的数据将会舍弃。此时,你可以将连...
INFILE "users_data.csv" --指定外部数据文件,可以写多个 INFILE "another_data_file.csv" 指定多个数据文件 // INFILE 'tt.date' // 导入多个文件 --这里还可以使用 BADFILE、DISCARDFILE 来指定坏数据和丢弃数据的文件, truncate --操作类型,用 truncate table 来清除表中原有记录 ...
Description: The BATCH_TABLE_ACCESS_BY_ROWID hint instructs the optimizer not use batch table access by rowid. SQL?? HelloDBA.com> alter session set "_optimizer_batch_table_access_by_rowid"=true; HelloDBA.com> exec sql_explain('select /*+NO_BATCH_TABLE_ACCESS_BY_ROWID(o)*/* from t...