2008年12月16日
打開Net Manager，選中服務名稱，檢查服務標識欄里的服務名輸入是否正確。該服務名必須與服務器端監聽器配置的全局數據庫名一致。
方法二： 在TOAD登陸時使用全局名稱：
zhouzhenhua:1521/javafan
人品不錯，挺讓人放心的，不會像有的男的看起來很花花的，還有就是沒有明顯的缺點，這可是很重要的
我現在看到的男的歪瓜裂棗的太多了
PL/SQL集合方法是用于操縱集合變量的內置函數或過程。
語法：
collection_name.method_name[(parameter)]
注意：集合方法extend和trim不適用于PL/SQL表。
1. exists
2. count
3. limit
返回VARRAY變量所允許的最大元素個數。嵌套表和PL/SQL表的元素個數無限制，所以調用該方法時返回NULL。
4. first和last
第一個元素的下標，最后一個元素的下標
ename_table(ename_table.first)
ename_table(ename_table.last)
5. prior和next
前一個元素的下標，后一個元素的下標
ename_table(ename_table.prior(1))
ename_table(ename_table.next(1))
6.extend
該方法為PL/SQL集合變量增加元素，只適用于嵌套表和VARRAY。
注意：當使用EXTEND增加元素時，不能為未初始化的集合變量增加元素。
EXTEND方法有三種調用方法：
- EXTEND:添加一個null元素。
- EXTEND(n):添加n個null元素
- EXTEND(n,i):添加n個元素，元素值與第i個元素相同。
7. trim
該方法用于從集合變量尾部刪除元素，并且只適用于嵌套表和VARRAY。
TRIM共有兩種調用方法：
- TRIM: 從集合變量尾部刪除一個元素。
- TRIM(n): 從集合變量尾部刪除n個元素。
8. delete
用于刪除特定元素，只適用于嵌套表和PL/SQL表。
DELETE有三種調用方法：
- DELETE: 刪除所有的元素
- DELETE(n): 刪除第n個元素。
- DELETE(m,n):刪除m~n之間所有的元素。
第一，PL/SQL表
它只能作為PL/SQL類型，不能作為表列類型。
下標可以為負值，并且元素個數無限制。
下標類型key_type: 包括BINARY_INTEGER、PLS_INTEGER、VARCHAR2。
語法：
TYPE type_name IS TABLE OF element_type
[NOT NULL] INDEX BY key_type;
identifier type_name;
例如：
DECLARE
TYPE category_table_type IS TABLE OF VARCHAR2 (40)
INDEX BY VARCHAR2 (40);
category_table category_table_type;
BEGIN
category_table ('長沙') := '長沙，我愛你！';
DBMS_OUTPUT.put_line (category_table ('長沙'));
END;
第二，嵌套表
可以作為表列的數據類型使用。
當使用嵌套表元素時，需要使用構造方法初始化嵌套表變量。
下標從1開始計算。
語法：
TYPE type_name IS TABLE OF element_type;
identifier type_name;
例子：
DECLARE
TYPE category_table_type IS TABLE OF tb_out_service.servicename%TYPE;
category_table category_table_type;
BEGIN
category_table := category_table_type ('全省', '長沙', '常德');
SELECT servicename
INTO category_table (3)
FROM tb_out_service
WHERE serviceid = '&serviceid';
DBMS_OUTPUT.put_line (category_table (1));
DBMS_OUTPUT.put_line (category_table (2));
DBMS_OUTPUT.put_line (category_table (3));
END;
第三，變長數組(VARRAY)
需要使用構造方法初始化VARRAY變量。
語法：
TYPE type_name is VARRAY(size_limit) OF element_type [NOT NULL];
identifier type_name;
第一，定義PL/SQL記錄
1. 自定義PL/SQL記錄
2. 使用%ROWTYPE屬性定義記錄變量
舉例：
-----------------------------------------------
DECLARE
--自定義記錄類型
TYPE emp_record_type IS RECORD (
serviceid tb_out_service%TYPE,
sericename tb_out_service%TYPE
);
emp_record emp_record_type;
--使用%ROWTYPE屬性定義記錄變量
category_record tb_out_service%ROWTYPE;
BEGIN
NULL;
END;
第二，使用PL/SQL記錄
DECLARE
--使用%ROWTYPE屬性定義記錄變量
category_r tb_out_service%ROWTYPE;
BEGIN
...
UPDATE tb_out_service
SET ROW = category_r --注意ROW關鍵字
WHERE serviceid = category_r.serviceid;
...
INSERT INTO tb_out_service
VALUES category_r; --在values子句中使用記錄成員播入數據。
...
END;
commit
rollback
savepoint a1
隱含游標：專門處理SELECT INTO、INSERT、UPDATE以及DELETE語句。
顯示游標：用于處理多行的SELECT語句。
當在PL/SQL塊中執行INSERT、UPDATE及DELETE語句時，為了取得DML語句作用的結果，需要使用SQL游標屬性。
第一，游標的4種屬性
1. SQL%ISOPEN
該屬性永遠都是false，沒有實際意義。
2. SQL%FOUND
語句是否操作成功。當SQL語句有作用行時為TRUE.
3. SQL%NOTFOUND
LOOP
FETCH emp_cursor INTO v_name, v_deptno;
EXIT WHEN emp_cursor%NOTFOUND;
...
END LOOP;
4. SQL%ROWCOUNT
返回SQL語句所作用的總計行數。
該屬性用于返回已提取的實際行數。
第二，顯示游標專用于處理SELECT語句返回的多行數據。
CURSOR cursor_name IS select_statement;
open cursor_name;
FETCH cursor_name INTO var1[, var2, ...];
CLOSE cursor_name;
例子：
DECLARE
CURSOR category_cursor
IS
SELECT *
FROM tb_out_service t
WHERE t.servicename LIKE '長沙%';
TYPE category_table_type IS TABLE OF tb_out_service%ROWTYPE
INDEX BY BINARY_INTEGER;
category_table category_table_type;
i INT;
BEGIN
OPEN category_cursor;
LOOP
i := category_cursor%ROWCOUNT + 1;
FETCH category_cursor
INTO category_table (i);
EXIT WHEN category_cursor%NOTFOUND;
DBMS_OUTPUT.put_line ( RPAD (category_table (i).serviceid, 30)
|| ' '
|| category_table (i).servicename
);
END LOOP;
CLOSE category_cursor;
END;
第三，游標FOR循環
語法：
FOR record_name IN cursor_name LOOP
statement;
...
END LOOP;
注意：當使用游標FOR循環時，既可以在定義部分定義游標，也可以直接在FOR循環中使用SELECT語句。
第四，參數游標
CURSOR cursor_name(parameter_name datatype) is select_statement;
OPEN cursor_name(parameter_value)
注意：
定義參數只能指定數據類型，不能指定長度。
另外，應該在游標的select語句的where子句中引用游標參數，否則失去了定義參數游標的意義。
---------------------------------------------------------------------------------------------------------------------
DECLARE
CURSOR category_cursor (NAME VARCHAR2)
IS
SELECT *
FROM tb_out_service t
WHERE t.servicename LIKE NAME || '%';
BEGIN
FOR category_record IN category_cursor ('吉首')
LOOP
DBMS_OUTPUT.put_line ( RPAD (category_record.serviceid, 30)
|| ' '
|| category_record.servicename
);
END LOOP;
END;
第五，更新或刪除游標行
語法：
CURSOR cursor_name IS select_statement
FOR UPDATE [OF column_reference] [NOWAIT];
UPDATE table_name SET column=.. WHERE CURRENT OF cursor_name;
DELETE FROM table_name WHERE CURRENT OF cursor_name;
注意：
1. OF子句的格式：column_reference為table_name.column_name
2. WHERE CURRENT OF cursor_name, 更新或者刪除游標所在行的數據。
3. 在使用游標更新或刪除數據時，定義游標必須帶有FOR UPDATE子句，并且在更新或者刪除游標時必須帶有WHERE CURRENT OF 子句。
當查詢語句涉及到多張表時，如果不帶有OF子句，會在多張表上同時加鎖，如果只在特定的表上加鎖，需要帶有OF子句。
DECLARE
CURSOR category_cursor (NAME VARCHAR2)
IS
SELECT *
FROM tb_out_service t
WHERE t.servicename LIKE NAME || '%'
FOR UPDATE OF t.querystr;
v_name CONSTANT VARCHAR2 (20) := '長沙';
BEGIN
FOR category_record IN category_cursor (v_name)
LOOP
IF INSTR (category_record.servicename, v_name || '——') <> 1
THEN
DBMS_OUTPUT.put_line ( 'delete: '
|| RPAD (category_record.serviceid, 30)
|| ' '
|| category_record.servicename
);
DELETE FROM tb_out_service
WHERE CURRENT OF category_cursor;
ELSE
DBMS_OUTPUT.put_line ( 'upate: '
|| RPAD (category_record.serviceid, 30)
|| ' '
|| category_record.servicename
);
UPDATE tb_out_service t
SET t.querystr = v_name || '——' || t.servicename
WHERE CURRENT OF category_cursor;
END IF;
END LOOP;
END;
第六， 游標變量
游標變量是基于REF CURSOR類型所定義的變量，它實際上是指向內存地址的指針。顯式游標只能定義靜態游標，而游標變量可以在打開時指定其所對應的SELECT語句，從而實現動態游標。
TYPE ref_type_name IS REF CURSOR [RETURN return_type];
cursor_variable ref_type_name;
OPEN cursor_name FOR select_statement;
FETCH cursor_variable INTO var1[, var2, ...];
CLOSE cursor_variable;
注意：
不能在遠程子程序中使用游標變量。
當指定子查詢時，不能帶有FOR UPDATE子句。
當指定RETURN子句時，返回類型必須使用PL/SQL記錄類型。
例子：
DECLARE
TYPE category_cursor_type IS REF CURSOR
RETURN tb_out_service%ROWTYPE;
category_cursor category_cursor_type;
category_record tb_out_service%ROWTYPE;
v_name CONSTANT VARCHAR2 (40) := '長沙';
BEGIN
OPEN category_cursor FOR
SELECT *
FROM tb_out_service t
WHERE t.servicename LIKE v_name || '%';
LOOP
FETCH category_cursor
INTO category_record;
EXIT WHEN category_cursor%NOTFOUND;
DBMS_OUTPUT.put_line ( RPAD (category_record.serviceid, 30)
|| ' '
|| category_record.servicename
);
END LOOP;
END;
編寫PL/SQL時，可以直接使用大多數的單行SQL函數，這些單行函數包括數字函數、字符函數、轉換函數及日期函數。
注意：某些SQL函數只能在SQL語句中引用，而不能直接在PL/SQL語句中引用，這些SQL函數包括GREATEST、LEAST、DECODE及所有的分組函數（如SUM）。
約束用于確保數據庫數滿足業務規則。
約束包括：NOT NULL，UNIQUE，PRIMARY KEY，FOREIGN KEY以及CHECK等5種類型。
建立主鍵約束和唯一約束時，Oralce會基于約束列自動建立唯一索引；主鍵約束不允許為NULL，唯一約束允許為NULL。
一張表只能建立一個主鍵約束。
建表約束：NOT NULL只能在列級定義；其它4種既可以在列級定義，也可以在表級定義。復合主鍵約束只能在表級定義。
維護約束：增加NOT NULL約束時必須使用MODIFY子句，而增加其它約束時需要使用ADD子句。
第一， 定義約束
---------------------------------------------
語法：
CREATE TABLE [SCHEMA.]table_name(
column_name datatype [DEFAULT expr] [column_constraint],
...
[table_constraint][, ...]
);
例子：
CREATE TABLE tt_user_info
(
ID VARCHAR2(20 BYTE),
NAME VARCHAR2(20 BYTE) NOT NULL,
category_id VARCHAR2(20 BYTE) REFERENCES tb_out_service(serviceid),
remark VARCHAR2(1000)
);
ALTER TABLE tt_user_info ADD (
CHECK ( LENGTH(NAME)>2),
PRIMARY KEY (ID),
UNIQUE (NAME)
);
說明：
1. NOT NULL，非空約束
not null
2. UNIQUE，唯一約束
UNIQUE (COL_NAME)
3. PRIMARY KEY，主鍵約束
primary key (col_name1 [, col_name2])
4. FOREIGN KEY，外鍵約束
它有三種類型：
references primary_table(primary_col)
on delete cascade
on delete set null
5. CHECK，檢查約束
check (money > 1000)
第二， 維護約束
----------------------------------------
1. 增加約束
NOT NULL使用ALTER MODIFY子句，其它的使用ALTER ADD子句
-------------------------------
CREATE TABLE tt_user(NAME VARCHAR2(20));
ALTER TABLE tt_user MODIFY user_name NOT NULL;
ALTER TABLE tt_user ADD CONSTRAINT constraint_name UNIQUE(NAME);
ALTER TABLE tt_user ADD CONSTRAINT constraint_name PRIMARY KEY(NAME);
ALTER TABLE tt_user ADD parentid VARCHAR2(20)
CONSTRAINT constraint_name
REFERENCES tb_out_service(serviceid);
2. 修改約束名
ALTER TABLE table_name RENAME CONSTRAINT old_constraint_name TO new_constraint_name
3. 刪除約束
ALTER TABLE table_name DROP CONSTRAINT constraint_name
4. 禁止約束
ALTER TABLE table_name DISABLE CONSTRAINT constraint_name [CASCADE];
5.激動約束
ALTER TABLE table_name ENABLE CONSTRAINT constraint_name;
第三. 顯示約束信息
所有約束信息
SELECT *
FROM user_constraints
用戶約束所對應的表列
SELECT *
FROM user_cons_columns;
臨時表分為兩種，它們只在事務或者會話內有效。
------------------------------------
A. 事務臨時表(缺省)：
CREATE GLOBAL TEMPORARY TABLE table_name(col_name INT);
CREATE GLOBAL TEMPORARY TABLE table_name(col_name INT) ON COMMIT DELETE ROWS;
------------------------------------
B. 會話臨時表：
CREATE GLOBAL TEMPORARY TABLE table_name(col_name INT) ON COMMIT PRESERVE ROWS;
A. 刪除數據
-----------------------------------------
方法一：
delete(DML)
只是刪除數據，并沒有釋放空間
操作可以回退
例如：
DELETE FROM table_name;
方法二：
truncate table(DDL)
刪除數據，釋放表空間，操作不能回退
例如：
TRUNCATE TABLE table_name;
B. 刪除庫表
------------------------------------------
DROP TABLE table_name [CASCADE CONSTRAINTS] [purge]
CASCADE CONSTRAINTS： 表示是否級聯刪除外鍵約束
C. 恢復刪除的庫表（10g）
FLASHBACK TABLE table_name TO BEFORE DROP;
當插入數據時，必須為NOT NULL列和主鍵列提供數據;
當復制大批量數據時，使用直接裝載的速度遠遠優于常規裝載。
使用常規裝載方式復制數據：
INSERT INTO table_name
SELECT *
FROM DUAL;
使用直接裝載方式復制數據：
INSERT INTO /*append*/ table_name
SELECT *
FROM DUAL;
*******************************************************************
1. ROUND
*******************************************************************
The ROUND function returns n rounded to m places right of the decimal point; if m is omitted, to 0 places. m can be negative to round off digits left of the decimal point. m must be an integer.
Syntax
PL/SQL Example
ROUND (153.46) ==> 153
ROUND (153.46, 1) ==> 153.5
ROUND (153, -1) ==> 150
SQL Examples
SELECT ROUND(15.193,1) "Round"
FROM DUAL
Round
----------
15.2
SELECT ROUND(15.193,-1) "Round"
FROM DUAL
Round
----------
20
*******************************************************************
2. TRUNC
*******************************************************************
The TRUNC function truncates the number supplied to the specified number of places. If no place number is supplied, it rounds to zero decimal places. If the place number is negative, the number is truncated that many places to the right of the decimal place. This function does no rounding, it simply deletes the un-wanted numbers and returns the rest.
Syntax
PL/SQL Example
TRUNC (153.46) ==> 153
TRUNC (153.46, 1) ==> 153.4
TRUNC (-2003.16, -1) ==> -2000
SQL Example
SELECT TRUNC(15.79,1) "Truncate"
FROM DUAL
Truncate
----------
15.7
SELECT TRUNC(15.79,-1) "Truncate"
FROM DUAL
Truncate
----------
10
*******************************************************************
3. INSTR
*******************************************************************
The INSTR functions search string for substring. The function returns an integer indicating the position of the character in string that is the first character of this occurrence. INSTR calculates strings using characters as defined by the input character set. INSTRB uses bytes instead of characters. INSTRC uses unicode complete characters. INSTR2 uses UCS2 codepoints. INSTR4 uses UCS4 codepoints.
position is an nonzero integer indicating the character of string where Oracle begins the search. If position is negative, Oracle counts and searches backward from the end of string.
occurrence is an integer indicating which occurrence of string Oracle should search for. The value of occurrence must be positive.
Both string and substring can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The value returned is of NUMBER datatype.
The default values of both position and occurrence are 1, meaning Oracle begins searching at the first character of string for the first occurrence of substring. The return value is relative to the beginning of string, regardless of the value of position, and is expressed in characters. If the search is unsuccessful (if substring does not appear occurrence times after the position character of string), the return value is 0.
Syntax
PL/SQL Example
Find the first occurrence of archie in “bug-or-tv-character?archie”:
INSTR ('bug-or-tv-character?archie', 'archie') ==> 21
The starting position and the nth appearance both defaulted to 1.
Find the first occurrence of archie in the following string starting from position 14:
INSTR ('bug-or-tv-character?archie', 'ar', 14) ==> 21
In this example a starting position was specified, which overrides the default of 1; the answer is still the same though. No matter where you start your search, the character position returned by INSTR is always calculated from the beginning of the string.
Find the second occurrence of archie in the following string:
INSTR ('bug-or-tv-character?archie', 'archie', 1, 2) ==> 0
There is only one archie in the string, so INSTR returns 0. Even though the starting point is the default, it cannot be left out if a nondefault nth appearance (2 in this case, for "second occurrence" ) is specified.
Find the second occurrence of "a" in "bug-or-tv-character?archie":
INSTR ('bug-or-tv-character?archie', 'a', 1, 2) ==> 15
The second "a" in this string is the second "a" in "character", which is in the fifteenth position in the string.
Find the last occurrence of "ar" in "bug-or-tv-character?archie".
INSTR ('bug-or-tv-character?archie', 'ar', -1) ==> 21
Use INSTR to confirm that a user entry is valid.
In the code below, we check to see if the command selected by the user is found in the list of valid commands. If so, that command is executed :
IF INSTR ('|ADD|DELETE|CHANGE|VIEW|CALC|', '|' || cmd || '|') > 0
THEN
execute_command (cmd);
ELSE
DBMS_OUTPUT.PUT_LINE
(' You entered an invalid command. Please try again...');
END IF;
SQL Examples
The following example searches the string "CORPORATE FLOOR", beginning with the third character, for the string "OR". It returns the position in CORPORATE FLOOR at which the second occurrence of "OR" begins:
SELECT INSTR('CORPORATE FLOOR','OR', 3, 2)
"Instring" FROM DUAL;
Instring
----------
14
The next example searches beginning with the third character from the end:
SELECT INSTR('CORPORATE FLOOR','OR', -3, 2)
"Reversed Instring"
FROM DUAL;
Reversed Instring
-----------------
2
This example assumes a double-byte database character set.
SELECT INSTRB('CORPORATE FLOOR','OR',5,2) "Instring in bytes"
FROM DUAL;
Instring in bytes
-----------------
27
*******************************************************************
4. SUBSTR
*******************************************************************
The substring functions return a portion of string, beginning at character position, substring_length characters long. SUBSTR calculates lengths using characters as defined by the input character set. SUBSTRB uses bytes instead of characters. SUBSTRC uses unicode complete characters. SUBSTR2 uses UCS2 codepoints. SUBSTR4 uses UCS4 codepoints.
If position is 0, it is treated as 1.
If position is positive, Oracle counts from the beginning of string to find the first character.
If position is negative, Oracle counts backwards from the end of string.
If substring_length is omitted, Oracle returns all characters to the end of string. If substring_length is less than 1, a null is returned.
string can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The return value is the same datatype as string. Floating-point numbers passed as arguments to SUBSTR are automatically converted to integers.
Syntax
PL/SQL Example
If the absolute value of the starting position exceeds the length of the input string, return NULL:
SUBSTR ('now_or_never', 200) ==> NULL
SUBSTR ('now_or_never', -200) ==> NULL
If starting position is 0, SUBSTR acts as though the starting position was actually 1:
SUBSTR ('now_or_never', 0, 3) ==> 'now'
SUBSTR ('now_or_never', 0) ==> 'now_or_never'
If the substring length is less than or equal to zero, return NULL:
SUBSTR ('now_or_never', 5, -2) ==> NULL
SUBSTR ('now_or_never', 1, 0) ==> NULL
Return the last character in a string:
SUBSTR ('Another sample string', -1) ==> 'g'
Remove an element from a string list.
This is, in a way, the opposite of SUBSTR: we want to extract a portion or substring of a string--and leave the rest of it intact. Suppose the screen maintains a list of selected temperatures, as follows:
|HOT|COLD|LUKEWARM|SCALDING|
The vertical bar delimits the different items on the list. When the user deselects "LUKEWARM," we now have to remove it from the list, which becomes:
|HOT|COLD|SCALDING|
The best way to accomplish this task is to determine the starting and ending positions of the item to be removed, and then use SUBSTR to take apart the list and put it back together without the specified item.
The list used in the above example contains 29 characters:
String: |HOT|COLD|LUKEWARM|SCALDING|
Character index: 1234567890123456789012345679
To extract this item from the list, we need to pull off the portion of the string before "LUKEWARM" as follows:
SUBSTR ('|HOT|COLD|LUKEWARM|SCALDING|', 1, 10)
and then we need to extract the trailing portion of the list (after "LUKEWARM"). Notice that we do not want to keep both of the delimiters when we put these pieces back together, so this next SUBSTR does not include the vertical bar at position 19:
SUBSTR ('|HOT|COLD|LUKEWARM|SCALDING|', 20)
We use the following concatenation of calls to SUBSTR:
SUBSTR ('|HOT|COLD|LUKEWARM|SCALDING|', 1, 10)
||
SUBSTR ('|HOT|COLD|LUKEWARM|SCALDING|', 20)
==>
'|HOT|COLD|SCALDING|'
Remove the middle word in a three-word string (in which each word is separated by an underscore) and switch the order of the first and last words.
FUNCTION bite_and_switch (tripart_string_in IN VARCHAR2)
RETURN VARCHAR2
IS
/* Location of first underscore */
first_delim_loc NUMBER := INSTR (tripart_string_in, '_', 1, 1);
/* Location of second underscore */
second_delim_loc NUMBER := INSTR (tripart_string_in, '_', 1, 2);
/* Return value of function, set by default to incoming string. */
return_value VARCHAR2(1000) := tripart_string_in;
BEGIN
/* Only switch words if two delimiters are found. */
IF second_delim_loc > 0
THEN
/* Pull out first and second words and stick them together. */
return_value :=
SUBSTR (tripart_string_in, 1, first_delim_loc - 1) || '_' ||
SUBSTR (tripart_string_in, second_delim_loc + 1);
END IF;
/* Return the switched string */
RETURN return_value;
END bite_and_switch;
SQL Examples
The following example returns several specified substrings of "ABCDEFG":
SELECT SUBSTR('ABCDEFG',3,4) "Substring"
FROM DUAL;
Substring
---------
CDEF
SELECT SUBSTR('ABCDEFG',-5,4) "Substring"
FROM DUAL;
Substring
---------
CDEF
Assume a double-byte database character set:
SELECT SUBSTRB('ABCDEFG',5,4.2) "Substring with bytes"
FROM DUAL;
Substring with bytes
--------------------
CD
*******************************************************************
5. RPAD
*******************************************************************
The RPAD or Right Pad function returns char1, right-padded to length n with char2, replicated as many times as necessary; char2 defaults to a single blank. If char1 is longer than n, this function returns the portion of char1 that fits in n.RPAD will also perform a trim function on the string if the specified length is less than the actual string length.
Both char1 and char2 can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The string returned is of VARCHAR2 datatype and is in the same character set as char1.
The argument n is the total length of the return value as it is displayed on your terminal screen. In most character sets, this is also the number of characters in the return value. However, in some multibyte character sets, the display length of a character string can differ from the number of characters in the string.
Syntax
PL/SQL Example
Display the number padded right with zeros to a length of 10:
RPAD ('55', 10, '0') ==> '5500000000'
You could also use TO_CHAR to convert from a number to a character:
TO_CHAR (55 * 10000000) ==> '5500000000'
Display the number padded right with zeros to a length of 5:
RPAD ('12345678', 5) ==> '12345'
RPAD interprets its padded_length as the maximum length of the string that it may return. As a result, it counts padded_length number of characters from the left (start of the string) and then simply returns that substring of the incoming value. This is the same behavior as that found with LPAD. Remember: RPAD does not return the rightmost five characters (in the above case "45678").
Place the phrase "sell!" after the names of selected stocks, up to a string length of 45:
RPAD ('HITOP TIES', 45, 'sell!')
==>
' HITOP TIESsell!sell!sell!sell!sell!sell!sell!'
Since the length of "HITOP TIES" is 10 and the length of "sell!" is 5, there is room for seven repetitions of the pad string. RPAD does, in fact, generate a repetition of the pattern specified in the pad string.
Place the phrase "sell!" after the names of selected stocks, up to a string length of 43:
RPAD ('HITOP TIES', 43, 'sell!')
==>
'HITOP TIESsell!sell!sell!sell!sell!sell!sel'
Because the length of "HITOP TIES" is 10 and the length of "sell!" is 5, there is no longer room for seven full repetitions of the pad string. As a result, the seventh repetition of "sell!" lost its last two characters.
Create a string of 60 dashes to use as a border in a report:
RPAD ('-', 60, '-')
==>
'------------------------------------------------------------'
SQL Example
The following example rights-pads a name with the letters "ab" until it is 12 characters long:
SELECT RPAD('MORRISON',12,'ab') "RPAD example"
FROM DUAL;
RPAD example
-----------------
MORRISONabab
英文解釋：
It is necessary to use an "escape" character to locate the characters '_' and '%' in a column. The keyword ESCAPE followed by the character used as the delimitor of choice is coded after the string search. For example, '+' is used as the escape character. For example:
SELECT NAME
FROM XYZ_TABLE
WHERE NAME LIKE 'XY+_Z+%BC%'ESCAPE '+'
Result: XY_Z%BCAA
...
XY_Z%BC99
The plus sign '+' can still be used as part of the search string as long as a '+' precedes it. For example:
SELECT NAME
FROM XYZ_TABLE
WHERE NAME LIKE 'XY++Z%' ESCAPE '+'
Result: XY+ZAAAAA
...
XY+Z99999
漢語解釋：
定義：escape關鍵字經常用于使某些特殊字符，如通配符：'%','_'轉義為它們原
來的字符的意義，被定義的轉義字符通常使用'\',但是也可以使用其他的符號。
實例：
SQL> select * from t11 where name like '%_%';
NAME
----------
aa_a
aaa
SQL> select * from t11 where name like '%\_%' escape '\';
NAME
----------
aa_a
注意：如果是 '/' 作為檢索字符, 必須 用 '/' 作為轉義符, 正斜扛也一樣.
select * from wan_test where psid like '%//%' escape '/'
懷孕了才知道老公很搞笑 ！
懷孕已經17周了，老公也越來越搞笑，他常常會趴在我肚子上問我，寶寶怎么沒反應？他還活著嗎？
我老公要和寶寶說話，每天只說三句：寶寶你好，我是你爸爸。我是好人。
寶寶4個月以后，我喊老公給兒子做胎教，他就趴在我肚皮上對寶寶用很像大灰狼的語調說：“蛋蛋你趕快給我睡覺！不然爸爸打你屁屁”這叫什么胎教啊！
我每次和老公發嗲，老公就貼著肚皮對寶寶說：踢你媽。
還有我每次躺著讓他數胎動，他都睡得特別快，真是催眠的好辦法。
現在寶寶動作大了，每天睡覺前有時可以看到肚皮明顯的滾動。老公看到總是很緊張，說寶寶，你在干嘛？然后摸摸肚子說，不要動了，快睡覺。如果哪天沒動，他又很緊張，左敲敲右敲敲說，寶寶，你動一下呀。
我每次跟老公說，寶寶又在踢我了。他就會很認真地說：等他出來我踢他，幫你報仇。
我老公聽我說了胎教的重要性之后一本正經地對寶寶說：“寶寶，我是爸爸，今天我們要講的主題是看電視。好，現在開始看電視，你要安靜點哦！”
我讓我老公唱歌給寶寶聽，他居然唱：我們是害蟲，我們是害蟲。
記得有一次做B超，老公跟著一起進去，當看到屏幕上寶寶在動時，他激動得連說話聲音都不一樣了。當看到寶寶那根長長的脊椎時，他居然興奮地說：哦，還有尾巴啊！
我看到一個奇怪的現象，就是看我貼子的一部分人，都在不久后做成了如下事情：
1、戀愛成功了； 2、生意談成了； 3、升官發財了； 4、心情舒暢了；
5、家庭和睦了； 6、身體健康了； 7、萬事順意了。
第一、學習struts2標簽文檔的順序
struts2標簽語法
struts-2.0.11.2/docs/docs/tag-syntax.html
OGNL語法
struts-2.0.11.2/docs/docs/ognl.html
標簽參考
struts-2.0.11.2/docs/docs/tag-reference.html
第二、容易搞混的符號：
%{...}: 顯示地表示表達式
#： 調用非根的上下文map中的值，如#request, #session, #attr等
@： 調用靜態方法或者靜態屬性
''： 用來表示字符串常量
""： html元素屬性值
舉例：
調用靜態屬性：
<s:property value="@全類名@serialVersionUID"/>
調用靜態方法：
<s:property value="@全類名@sayHello()"/>
第三、使用debug調試標簽
<s:debug/>
第四、action的測試junit測試用例的編寫方法
新建action
填入參數
執行action方法，比如execute()
assert輸出結果
第五、自定義struts2標簽
AbstractUITag
ComponentTagSupport
HiddenTag
Hiddeng
ftl模塊文件
1. 在web.xml中不需要同struts1般部署FreeMarker了;原因網上說是由于Struts2本身便集成了FreeMarker,< <Struts2權威指南>>一書說是Struts2的標簽本身就是用FreeMarker編寫的.
2. 由于 ftl 文件默認編碼為 GBK,但頁面上無法顯示,后經高手指點----需在項目屬性中將 Text file encoding 編碼改為 UTF-8.
3. 在 struts.xml 配置文件中跳轉到 ftl 頁面時,需要在 <result >中添加 type="freemarker ">您要跳轉的ftl頁面</result>
1.頁面編碼統一utf-8
2.獲取值的時候將iso8859-1轉換成utf-8
或者做個過濾器，將頭設置成utf-8
3.數據庫編碼是utf-8，連接的時候也制定utf-8
4.tomcat里面的server.xml 里面設置URIEncoding="UTF-8"
一.什么是重構？
A series of small steps, each of which changes the program’s internal structure without changing its external behavior。
重構是一系列的小部驟,每一步只修改程序的內部結構,但是不改變它的外部行為.
二.為什么要重構
- To improve the software design
- 為了提高軟件設計
-Combat's "it rot"
抵抗代碼的腐化
-Makes the program easier to change
使程序更容易修改
- To make the software easier to understand
- 使軟件更容易理解
-Write for people, not the compiler
程序是寫給人看的,不是給編譯器看的.
-Understand unfamiliar code
理解不熟悉的代碼
- To help find bugs
- 幫助找到bug
-Refactor while debugging to clarify the code
在為了理清代碼而DEBUG時,進行重構.
三.我們應該在什么時候重構?
- To add new functionality
- 添加新的功能時
-Refactor existing code until you understand it
重構現有的代碼直到你理解它們
-Refactor the design to make it easy to add
重構設計使它容易添加新的功能
-Refactor to understand the code
重構直到你理解代碼
-Rmmediate effect of code review
-Allows for higher level suggestions
Don’t set aside time for refactoring,include it in your normal activities
在日常活動中進行重構,而不是另外找時間去重構.
四.最后的思想
-
The one benefit of objects is that they make it easier to change.
-
有一個好處就是使得對象更容易修改.
-
Refactoring allows you to improve the design after the code is written
-
重構允許你在代碼已經寫完后改進自己的設計.
-
Up front design is still important,but not so critical
-
事先的設計仍然是很重要的,但是并不那么關鍵了.
五.例子中用到的的重構條目:
Find temp with a single assignment
Extract Right Hand Side of assignment
Replace all references of temp with new method
Remove declaration and assignment of temp
Compile and test
Create method named after intention of code
Copy extracted code
Look for local variables and parameters
Turn into parameter
Turn into return value
Declare within method
Compile
Replace code fragment with call to new method
Compile and test
Declare method in target class
Copy and fit code
Set up a reference from the source object to the target
Turn the original method into a delegating method
-amountOf(Rental each) {return each.charge()}
-Check for overriding methods
Compile and test
Find all users of the method
-Adjust them to call method on target
Remove original method
Compile and test
Create a new state class for the type code
Add subclasses of the state object, one for each type code
Create an abstract query in the superclass to return the type code. Override in subclasses to return correct type code
Compile
Create field in old class for the state object
Change the type code query to delegate to the state object
Change the type code setting methods to assign an instance of the subclass
Compile and test
Move switch to superclass of inheritance structure
Copy one leg of case statement into subclass
Compile and test
Repeat for all other legs
Replace case statement with abstract method
Take two methods with similar overall structure but varying pieces
Use subclasses of current class, or create a strategy and move the methods to the strategy
At each point of variation extract methods from each source with the the same signature but different body
Declare signature of extracted method in superclass and place varying bodies in subclasses
When all points of variation have been removed,move one source method to superclass and remove the other
六.例子中提到的模式:
策略模式
模版方法模式
狀態模式