http://blog.gregwym.info/tag/sql/ http://blog.gregwym.info/db2-shu-ju-ku-dao-chu-he-dao-ru.html 2011-11-04T03:48:05+08:00 Db2=>CONNECT TO db_name Db2=>EXPORT TO absolute_file_path OF DEL SELECT * FROM "table_name" Db2=>IMPORT FROM absolute_file_path OF DEL INSERT_UPDATE INTO "table_name" http://blog.gregwym.info/sql-yu-fa-zheng-li.html 2011-10-17T06:00:15+08:00 SELECTSELECT attribute-expression-list FROM relation-list [ WHERE condition ]; attribute-expression-list: [relation-name.]attribute [relation-name.]attribute [arithmatic computation] AS another name i.e., E.Salary - 40000 AS SalaryDiff CASE WHEN ... THEN ...ELSE ... END i.e., CASE WHEN E.Salary < 40000 THEN 0ELSE E.Salary - 40000 END relation-list: list of table names seperate by comma condition: arithmetic operation +, -, *, / comparisions =, <>, <, <=, >. >= logical connectives AND, OR, NOT attribute IN (Q) attribute NOT IN (Q) attribute op SOME (Q) attribute op ALL (Q) EXISTS (Q) NOT EXISTS (Q) IS [NOT] NULL NULLAND Table AND TRUE FALSE NULL TRUE TRUE FALSE NULL FALSE FALSE FALSE FALSE NULL NULL FALSE NULL OR Table OR TRUE FALSE NULL TRUE TRUE TRUE TRUE FALSE TRUE FALSE NULL NULL TRUE NULL NULL NOT Table NOT TRUE FALSE NULL FALSE TRUE NULL UNION INTERSECT EXCEPT(Q1 and Q2 must have same attribute-list)Q1 UNION Q2 => Together all the tuples in Q1 and Q2Q1 INTERSECT Q2 => Only tuples in both Q1 and Q2Q1 EXCEPT Q2 => Tuples only in Q1 but not in Q2ALL关键字: 允许重复UNION ALL will include twice of duplicate tuplesINTERSECT ALL will include all possible pairs of match tuples, duplication possibleEXCEPT ALL will include all "not in Q2" tuples, duplication possible[INNER]/OUTER JOIN Inner join把两个表连接在一起, 返回两个表中相匹配的记录, 是2和3的交集 Left outer join, 左侧表所有的记录都返回, 右侧匹配的记录返回, 没有匹配的返回Null Right outer join, 与Left outer join相反, 右侧的记录返回, 左侧返回匹配的记录, 没有匹配返回Null Full outer join, 2和3的并集 Cross join, 两个表的笛卡儿积, 返回所有可能的值, 不允许有连接条件 ORDER BYSELECT ... ... ORDER BY attribute [DESC/ASC], attribute [DESC/ASC], ...... Note: 如果没有指定Order, return的数据可能是任意顺序GROUP BY, HAVING, Aggregate expressions{count, sum, avg, min, max} => Aggregate expressionsOrder: Group => Having => Aggregate count(*): number of tuples count(E): number of tupple for which E is non-NULL count(distinct E): number of distinct non-NULL E values sum(E) sum(distinct E) avg(E) avg(distinct E) min(E) max(E) Note: 没有被group by指定的attribute不能出现在SELECT的attr-list中, 除非是aggregateINSERT INTOINSERT INTO relation-name [( attribute-list )] VALUE ( value-list ); DELETEDELETE FROM relation-name [ WHERE condition ]; UPDATEUPDATE relation-name SET attribute-assignment-list [ WHERE condition ]; attribute-assignment-list: pairs of assignment seperate by comma i.e., WorkDept = 'E01', Address = 'Waterloo' CREATE TABLECREATE TABLE relation-name ( attribute-name attribute-type [constraints-list], ... ) attribute-type: http://www.w3school.com.cn/sql/sql_datatypes.aspconstraints-list: (Constraints的格式在各种数据库中都不太一样, 就不列举了) NOT NULL PRIMARY KEY UNIQUE FOREIGN KEY Column or Tuple CHECK CREATE VIEWCREATE VIEW view-name AS ( SELECT ... ) 从View SELECT的方法和table一样CREATE TRIGGERCREATE TRIGGER trigger-name AFTER UPDATE OF attribute-list ON relation-name REFERENCING OLD as instance-name(o) NEW as instance-name(n) FOR EACH ROW ... 不同database语法不一