DB2-ORACLE字符与数字类型装换.docx

DB2中字符、数字和日期类型之间的转换一般我们在使用DB2或Oracle的过程中,经常会在数字字符日期三种类 型之间做转换,那么在DB2和Oracle中,他们分别是如何实现的呢?在Oracle这几个类型之间的转换是十分方便的，通过 to_char|to_date|to_number函数即可完成类型转换。本小节主要介绍DB2中的一些知识，从Oracle转过来的DBA或开发人 员，可以对比着学习。数字型到字符型的转换DB2中的col_a字段字段类型到字符类型的转换smallintchar(col_a)integerbigintdoublechar(cast(col_a as decimal(8,2)decimal(8,2)Digits(col_a)测试一下：SQLcreate table test_datatypeSQL(SQLcol_a smallint,SQLcol_b integer,SQLcol_c bigint,SQLcol_d decimal(8,2),SQLcol_e doubleSQL);DB20000I SQL命令成功完成。SQLinsert into test_datatype values(1,20,3000,4000.44,55555);DB20000I SQL命令成功完成。SQLdescribe select * from test_datatype列信息 列数：5 SQL 类型 类型长度 列名 名称长度 - - - - 501 SMALLINT 2 COL_A 5 497 INTEGER 4 COL_B 5 493 BIGINT 8 COL_C 5 485 DECIMAL 8, 2 COL_D 5 481 DOUBLE 8 COL_E 5SQLselect * from test_datatype;COL_A COL_B COL_C COL_D COL_E- - - - - 1 20 3000 4000.44 +5.55550000000000E+004 1 条记录已选择。SQLselect char(col_a),char(col_b),char(col_c),digits(col_d),char(cast(col_e as decimal(8,2) from test_datatype;1 2 3 4 5- - - - -1 20 3000 00400044 055555.00 1 条记录已选择。SQLselect char(col_a)|,|char(col_b)|,|char(col_c)|,|digits(col_d)|,|char(cast(col_e as decimal(8,2) from test_datatype;1-1 ,20 ,3000 ,00400044,055555.00 1 条记录已选择。SQL字符型到数字型的转换DB2中的col_a字段字段类型数字类型转换charsmallintInteger(trim(char(col_a)integerbigintcast(char(col_a) as bigint)decimalcast(col_a as decimal(8,2)doublecast(cast(char(cast(a.col_a as decimal(8,2) as decimal(8,2) as double)测试一下SQLcreate table test_datatypeSQL(SQLcol_a char(2),SQLcol_b char(4),SQLcol_c char(10),SQLcol_d char(10),SQLcol_e char(10)SQL);DB20000I SQL命令成功完成。SQLinsert into test_datatype values(1,200,30000,4000.04,5000000);DB20000I SQL命令成功完成。SQLdescribe select * from test_datatype;列信息 列数：5 SQL 类型 类型长度 列名 名称长度 - - - - 453 CHARACTER 2 COL_A 5 453 CHARACTER 4 COL_B 5 453 CHARACTER 10 COL_C 5 453 CHARACTER 10 COL_D 5 453 CHARACTER 10 COL_E 5SQLselect Integer(trim(char(col_a),SQLInteger(trim(char(col_b),SQLcast(char(col_c) as bigint),SQLcast(col_d as decimal(8,2),SQLcast(cast(char(cast(col_e as decimal(12,2) as decimal(12,2) as double)SQLfrom test_datatype;1 2 3 4 5- - - - - 1 200 30000 4000.04 +5.00000000000000E+006 1 条记录已选择。SQL字符型到日期时间型的互换DB2中的col_a字段字段类型日期时间型chardate(trim(char(col_a)timestamp(trim(char(col_a)或to_date(-string-expression,format-string(DB2 9)注：to_date实际是TIMESTAMP_FORMAT函数的一个同义词字段类型字符类datechar(col_a)timetimestampchar(col_a) 或 to_char(-timestamp-expression-,format-string-) (DB2 9)注：to_char实际是VARCHAR_FORMAT函数的一个同义词测试一下看看SQLselect date(trim(char(2009-09-01 ),SQLtime(trim(char(12:23:34 ),SQLtimestamp(trim(char(2009-02-26-14.28.40.234000) from sysibm.dual;1 2 3- - -2009-09-01 12:23:34 2009-02-26-14.28.40.234000 1 条记录已选择。SQLselect char(current date),char(current time),char(current timestamp) from sysibm.dual;1 2 3- - -2009-02-26 14:28:40 2009-02-26-14.28.40.234000 1 条记录已选择。SQLselect to_char(current timestamp,yyyy-mm-dd hh24:mi:ss) from sysibm.dual;-DB2 9版本中新增1-2009-