ORACLE SQL Fundamental I 1-4 章重點 Chap 1 Introduction Chap 2 Retrieving Data Using the SQL SELECT Statement Chap 3 Restricting and Sorting Data Chap 4 Using Single-Row Functions to Customize Output

軟體： Oracle DB 11g Enterprise  從 下載  Oracle DB 11g Enterprise, 包含 HR 的資料  HR 資料用於範例說明及上機實習  安裝時 1. 下載的檔案要先解壓縮 2.HR 的帳號要解鎖, 且設密碼 ( 如 : hr 或 Oracle11g ) P.S. 1.Oracle DB 11g Express 2.Oracle DB 12c 為雲端的資料庫 2

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第一種編輯軟體 ─ ─ SQLdeveloper  安裝 SQLdeveloper ： 1. 從 / downloads /developer tools 下載 2. 須先安裝 JDK ( 版本不要太新, 1.6 版即可 ) 3. 進入 SQLdeveloper, 連線登入時需輸入 SID( 資料庫 ) 1)orcl : 11g Enterprise 2)xe : 11g Express » 右鍵 /property/save 密碼  執行 SQLdeveloper ： 1. 先執行桌面的『 Open Oracle Service 』 2. 再執行桌面的『 sqldeveloper 』 3. 進入 SQLdeveloper 後，點選左邊視窗的 hr ，密碼輸入 hr 4

第二種編輯軟體 ─ ─ SQLPLUS  SQLPLUS ：  在『命令提示字元』 (DOS 環境 ) 直接下指令 C:>sqlplus hr/hr SQL> select * from hr.employees; SQL> select table_name from user_tables; …….. 離開 SQLPLUS ……………. SQL> exit 或使用管理者進去 C:>sqlplus sys/oracle as sysdba SQL> alter user hr identified by hr account unlock; 5

更改密碼 SQL> alter user 帳號 identified by 密碼 ; 6

1-20Data Models 7

1-23 Entity Relationship Model  實體間的關係 :  Assign one or more employees to a department  Some departments do not yet have assigned employees  屬性 :  Mandatory( 強制 ) marked with 『 * 』 ( 一定要輸入 )  optional ( 選項 ) marked with 『 o 』  Primary( 主鍵 ) marked with 『 # 』 8

Relationship - Hyphen 連接號 -- dash 破折號 / slash 斜線 \ backslash 反斜線 # hash sign

1-25 Relating Multiple Tables  Primary key: 主鍵  Foreign key: 外來鍵 10

Introduction Updates, inserts, or deletes a row conditionally into/from a table

1-34 補充 14

Retrieving Data Using the SQL SELECT Statement  Projection:  Selects the columns in a table that are returned by a query  Selection:  Selects the rows in a table that are returned by a query  Joins:  Brings together data that is stored in different tables by specifying the link between them

SELECT {*|[DISTINCT] column|expression [alias],...} FROM table;  * 選擇全部欄位  DISTINCT Suppresses duplicates  重複值只取一個  SQL 指令不分大小寫 (not case sensitive)  SQL 指令以 ; (semicolon) 結束 ， SQL*Plus 一定要加『 ; 』  Run Script icon 或 [F5] ： ( 執行全部指令 )  run the command or commands in the SQL Worksheet  executes all the statements in the Enter SQL Statement box  Execute Statement icon 或 press [F9] ： ( 執行指標所指的指令 )  run a SQL statement in the SQL Worksheet  executes the statement at the mouse pointer in the Enter SQL Statement box 有 DISTINCT 時, SELECT 只能列一個欄位

 SQL Developer:  標題（ heading ）預設靠左（ Left-aligned ）  標題大寫 (Uppercase) SELECT last_name, hire_date, salary FROM employees;  SQL*Plus:  標題（ heading ）：  字元 (Character) 和日期 (Date) 靠左（ Left-aligned ）  數字 (Number) 靠右 (right-aligned)  標題大寫 (Uppercase)

 Arithmetic Expressions (+, -, *, / ) 可用於：  數字 (Number)  日期 (Date)  DATE 和 TIMESTAMP 只能用 + 和 -  除了 From 子句  Oracle Server 會忽略運算子前後的空白（ blank spaces ）  NULL 是 unavailable, unassigned, unknown, or inapplicable  NULL 不是 0 也不是空白 (blank space) 2-14

SELECT last_name, 12*salary*commission_pct FROM employees;  Arithmetic expressions containing a null value evaluate to null  null 做運算 (+-*/) 後還是 null  例如 :  除以 0(division by zero) 會產生錯誤  但，除以 null (divide a number by null), 結果還是 null 或 unknown

 alias （別名） :  緊接在欄位後  可使用 AS  若別名包含空白、特殊字元、大小寫  以「 " " 」雙引號 (double quotation marks) 括住  且有分大小寫 SELECT last_name "Name", salary*12 "Annual Salary" FROM employees; p.s. 若 alias 沒以雙引號括住，則標頭列印時, 為大寫

2-18 SELECT last_name AS name, commission_pct comm FROM employees; SELECT last_name "Name", salary*12 "Annual Salary" FROM employees; 21

補充 :106. View the Exhibit and examine the description of the EMPLOYEES table. Your company wants to give 5% bonus to all the employees on their annual salary. The SALARY column stores the monthly salary for an employee. To check the total for annual salary and bonus amount for each employee, you issued the following SQL statement: SELECT first_name, salary, salary*12+salary*12*.05 "ANNUAL SALARY + BONUS" FROM employees; Which statement is true regarding the above query? A. It would execute and give you the desired output. B. It would not execute because the AS keyword is missing between the column name and the alias. C. It would not execute because double quotation marks are used instead of single quotation marks for assigning alias for the third column. D. It would execute but the result for the third column would be inaccurate because the parentheses for overriding the precedence of the operator are missing. Answer: A 22 題庫 106 公司要給所有員工年薪 5% 的獎金, SALARY 為月薪 別名 alias 別名之前的 AS 可省略 double quotation marks 雙引號 是對的 這裡不加括弧 (parentheses) 沒關係

 Concatenation Operator （連接運算子）：  two vertical bars (||)  連接 columns 或 字串  concatenate 字串和 null, 結果為字串  LAST_NAME || NULL 結果是 LAST_NAME  date 型態也可以做 concatenate  Date 和 character literal values 必須包含在單引號『 ' ' 』中 SELECT last_name || ' is a ' || job_id AS "Employee Details" FROM employees; 2-21

 Alternative Quote (q) Operator  指定自己的 quotation mark delimiter( 定義符號 )  mark delimiter 可以是 single-byte or multibyte, or any of the following character pairs: [ ], { }, ( ), or SELECT department_name || q'[ Department's Manager Id: ]' || manager_id AS "Department and Manager" FROM departments;

補充 :104. SELECT product_name || 'it's not available for order' FROM product_information WHERE product_status = 'obsolete'; You received the following error while executing the above query: ERROR: ORA-01756: quoted string not properly terminated What would you do to execute the query successfully? A. Enclose the character literal string in the SELECT clause within the double quotation marks. B. Do not enclose the character literal string in the SELECT clause within the single quotation marks. C. Use Quote (q) operator and delimiter to allow the use of single quotation mark in the literal character string. D. Use escape character to negate the single quotation mark inside the literal character string in the SELECT clause. Answer: C 25 題庫 104 常數字串必須包含在單引號『 ‘ ’ 』中, 但若常數字串本身已內含單引號, 就要指定自己的 quotation mark delimiter 更正為 : SELECT product_name || q'[it's not available for order]' FROM product_information WHERE product_status = 'obsolete';

 DISTINCT ：去除重複值 SELECT DISTINCT department_id FROM employees;  不加 DISTINCT ： SELECT department_id FROM employees; SELECT DISTINCT department_id, employee_id FROM employees; 沒有去除重複資料 去除重複資料

 DESCRIBE ：  可以簡寫為 DESC  顯示 table 的結構

 NUMBER(p,s)  Number value having a maximum number of digits p, with s digits to the right of the decimal point  最長 p 位，小數 s 位  VARCHAR2(s)  Variable-length character value of maximum size s  變動長度字串，最長 s 位

2-28 Quiz  Identify the two SELECT statements that execute successfully. 29

Restricting and Sorting Data SELECT employee_id, last_name, job_id, department_id FROM employees WHERE department_id = 90 ;  where 子句不可使用別名

 數字常數：  不需要用單引號  字串：  為 case-sensitive ( 有分大小寫 )  字串及日期值：  須用單引號括起來 SELECT last_name FROM employees WHERE hire_date = '17-FEB-96' ;  錯誤 : 不是有效的月份  查詢現在的日期及格式： select sysdate from dual; SELECT last_name,hire_date FROM employees WHERE hire_date = '07-6 月 -02' ;  date 為 format-sensitive ( 有分日期格式 )  預設 date 顯示格式為 DD-MON-RR Alter session set nls_date_format =‘YYYY-MM-DD:HH24:MI:SS’; Alter session set nls_date_language =American; NLS : National Language Support

 比較運算子（ Comparison Operators ）：  不等於可用 <>, !=, ^=

 between 低 and 高  包含最低和最高值  且須先寫最低值  可用於數字、字串 SELECT last_name, salary FROM employees WHERE salary BETWEEN 2500 AND 3500 ; SELECT last_name FROM employees WHERE last_name BETWEEN 'King' AND 'Smith' ; 若改為 BETWEEN 3500 AND 2500 語法沒有錯誤, 但結果不對  找不 到資料

 in (.,.,.)  括號內的值, 不用按順序排列  可用於任何型態  oracle 內部是使用 or 來處理 in, 所以, in 沒有效率優勢 SELECT employee_id, last_name, salary, manager_id FROM employees WHERE manager_id IN (100, 101, 201) ; 相當於 WHERE manager_id =100 or manager_id =101 or manager_id =201

 LIKE  萬用字元（ wildcard ）搜尋  % ： 0 或多個字元  _ ：一個字元 SELECT first_name FROM employees WHERE first_name LIKE 'S%' ;  尋找 January, 2002 and December, 2002 期間進公司的員工 SELECT last_name, hire_date FROM employees WHERE hire_date LIKE '%02' ;

 % 和 _ 並用： SELECT last_name FROM employees WHERE last_name LIKE '_o%' ;  若要找的字剛好是萬用字元 % 或 _, 則需用 escape '\' 來識別 SELECT job_id FROM jobs WHERE job_id LIKE '%SA\_%' ESCAPE '\'

 NULL Conditions ：  WHERE 子句  要用 is null  不可以用 = null SELECT last_name, manager_id FROM employees WHERE manager_id IS NULL ; SELECT last_name, manager_id FROM employees WHERE manager_id = NULL ; SELECT last_name, manager_id FROM employees WHERE manager_id IS NOT NULL ; 語法沒有錯誤 但結果不對  找不到資料

 AND Truth Table （強勢 : false > null > true ）  TRUE AND NULL = NULL  FALSE AND NULL = FALSE  NULL AND NULL = NULL SELECT employee_id, last_name, job_id, salary FROM employees WHERE salary >= AND job_id LIKE '%MAN%' ;

 OR Truth Table （強勢 : true > null > false ）  NULL or FALSE = NULL  NULL or NULL = NULL  NULL or TRUE = TRUE SELECT employee_id, last_name, job_id, salary FROM employees WHERE salary >= OR job_id LIKE '%MAN%' ;

補充 :23. display PRODUCT_NAME from the table where the CATEGORY_ID column has values 12 or 13, and the SUPPLIER_ID column has the value SELECT product_name FROM product_information WHERE (category_id = 12 AND category_id = 13) AND supplier_id = ; A. It would execute but the output would return no rows. B. It would execute and the output would display the desired result. C. It would not execute because the entire WHERE clause condition is not enclosed within the parentheses. D. It would not execute because the same column has been used in both sides of the AND logical operator to form the condition. Answer: A 40 題庫 23 查詢 CATEGORY_ID 欄位值 12 or 13, 且 SUPPLIER_ID 為 的產品名稱 (PRODUCT_NAME) 產品的類別 CATEGORY_ID 欄位值不可能既為 12 又為 13, 所以查出來為 NULL 值

 NOT... WHERE job_id NOT IN ('AC_ACCOUNT', 'AD_VP')... WHERE salary NOT BETWEEN AND WHERE last_name NOT LIKE '%A%'... WHERE commission_pct IS NOT NULL

 Rules of Precedence （優先順序）

SELECT last_name, job_id, salary FROM employees WHERE job_id = 'SA_REP' OR job_id = 'AD_PRES' AND salary > 15000; SELECT last_name, job_id, salary FROM employees WHERE ( job_id = 'SA_REP' OR job_id = 'AD_PRES' ) AND salary > 15000; 先做 AND, 再做 OR 用括弧, 使 OR 先做, 再做 AND

order by  order by  排序, 一定要在 select 敘述的最後  可以用別名 SELECT employee_id, last_name, salary*12 annsal FROM employees ORDER BY annsal  可以用運算式 SELECT employee_id, last_name, salary*12 annsal FROM employees ORDER BY salary*12  若沒用 order by, 則每次輸出順序可能都不一樣  ASC: Ascending ，預設由小到大，可省略  DESC: Descending ，由大到小  order by 的欄位 : 不用一定要出現在 select lists Where 及 group by 不可用別名

3-24 order by  ASC : null 值放後頭 select commission_pct from employees order by commission_pct ;  DESC: null 值放前頭 select commission_pct from employees order by commission_pct desc ; 45

補充 :7. the product names and the date of expiration of warranty for all the products, if the product is purchased today. The products that have no warranty should be displayed at the top and the products with maximum warranty period should be displayed at the bottom. 46 題庫 7 查詢產品名稱及保證到期日, 假設產品今天購買, 最大的 產品保證到期日放在後面

補充 :7.( 續 ) A. SELECT product_name, SYSDATE+warranty_period AS "Warranty expire date" FROM product_information ORDER BY SYSDATE-warranty_period; B. SELECT product_name, SYSDATE+warranty_period AS "Warranty expire date" FROM product_information ORDER BY SYSDATE+warranty_period; C. SELECT product_name, SYSDATE+warranty_period AS "Warranty expire date" FROM product_information ORDER BY SYSDATE; D. SELECT product_name, SYSDATE+warranty_period "Warranty expire date" FROM product_information WHERE warranty_period > SYSDATE; Answer: B 47 題庫 7 更正為 : ORDER BY SYSDATE+warranty_period;

order by  控制 null 順序 :  NULLS FIRST:  若有 row 含 NULL 值, 則放在最前面 select commission_pct from employees order by commission_pct nulls first ;  NULLS LAST:  若有 row 含 NULL 值, 則放在最後面 select commission_pct from employees order by commission_pct desc nulls last ;

 以欄位的數字位置（ column’s numeric position ）排序： SELECT last_name, job_id, department_id, hire_date FROM employees ORDER BY 3 ;  多個欄位排序 SELECT last_name, department_id, salary FROM employees ORDER BY department_id, salary DESC; 亦即以 department_id 做排序 department_id 以 ASC 做排序 salary 以 DESC 做排序

補充 :70. SELECT product_name, list_price, min_price, list_price - min_price Difference FROM product_information sorted output in ascending order of the price difference between LIST_PRICE and MIN_PRICE? (Choose all that apply.) A. ORDER BY 4 B. ORDER BY MIN_PRICE C. ORDER BY DIFFERENCE D. ORDER BY LIST_PRICE E. ORDER BY LIST_PRICE - MIN_PRICE Answer: A C E 50 題庫 70 將 LIST_PRICE and MIN_PRICE 的 price difference ( 差額 ) 做升冪排序

補充 :58. SELECT first_name, department_id, salary FROM employees ORDER BY department_id, first_name, salary desc; Which two statements are true regarding the output of the above query? (Choose two.) A. The values in all the columns would be sorted in the descending order. B. The values in the SALARY column would be sorted in descending order for all the employees having the same value in the DEPARTMENT_ID column. C. The values in the FIRST_NAME column would be sorted in ascending order for all the employees having the same value in the DEPARTMENT_ID column. D. The values in the FIRST_NAME column would be sorted in the descending order for all the employees having the same value in the DEPARTMENT_ID column. E. The values in the SALARY column would be sorted in descending order for all the employees having the same value in the DEPARTMENT_ID and FIRST_NAME column. Answer: C E 51 題庫 58 先以 department_id 升冪排序, 當 department_id 值相同時, 再以 first_name 升冪排序, 當 first_name 值相同時, 再以 salary 降冪排序

52 SQL 執行順序 from  where  group by  having  select  order by

 Substitution Variables （代入變數）使用於： 1.WHERE conditions 2.ORDER BY clauses 3.Column expressions 4.Table names 5.Entire SELECT statements  變數值可從以下幾種方式而得 1.file 2.Person 3. 另一個 select statement

單一的 &  單一的 &  每一次都會提示使用者輸入  數值型態 : SELECT employee_id, last_name, salary, department_id FROM employees WHERE employee_id = &employee_num ; 113

單一的 &  date 和 character 值要用單引號括起來 SELECT last_name, department_id, salary*12 FROM employees WHERE job_id = '&job_title' ; IT_PROG

單一的 & SELECT employee_id, last_name, job_id, &column_name FROM employees WHERE &condition ORDER BY &order_column ; salary Salary >15000 last_name

&&  &&  可 reuse 變數  只需提示一次, 不用每次提示輸入  且若再執行一次 query 時, 不會再被提示 SELECT employee_id, last_name, job_id, &&column_name FROM employees ORDER BY &column_name ; department_id

&&  DEFINE  新增變數並指定變數值  UNDEFINE  移除變數  substitution variable 存在  直到 undefine 該變數或離開該 session DEFINE employee_num = 200 ; SELECT employee_id, last_name, salary, department_id FROM employees WHERE employee_id = &employee_num ; UNDEFINE employee_num ;

 使用 SET VERIFY ON  顯示取代變數前與後的值 SET VERIFY ON SELECT employee_id, last_name, salary FROM employees WHERE employee_id = &employee_num;

3-37 Quiz  Which four of the following are valid operators for the WHERE clause? a. >= b. IS NULL c. != d. IS LIKE e. IN BETWEEN f. <> 60

及 4-5 Using Single-Row Functions to Customize Output  SQL function ： 不一定有參數, 但一定會回傳一個值  Two Types of SQL Functions 1.Single-row function : 作用在單一列, 且每列回傳一個值 2.Multiple-Row Functions : 作用在一組列中, 每一組回傳一個值, 又 稱為 group functions

Single-Row Functions  Single-Row Functions ：  修改資料型態  nested( 巢狀 )  參數可以是欄位或運算式（ expression ）  可用在 1.Select 2.Where 3.Order by

Single-Row Functions  Character functions:  輸入 character, 回傳 both character and number 值  Number functions:  輸入 numeric ，回傳 numeric 值  Date functions:  操作在 DATE data type  MONTHS_BETWEEN function, 回傳 number  其餘回傳 DATE 值  Conversion functions:  轉換 data type to another  General functions:  NVL  NVL2  NULLIF  COALESCE  CASE  DECODE

Character Functions INITCAP ： 第一個字母大寫

4-11 SELECT 'The job id for ' || UPPER(last_name) || ' is ' || LOWER(job_id) AS "EMPLOYEE DETAILS" FROM employees; 65

4-12 SELECT employee_id, last_name, department_id FROM employees WHERE LOWER(last_name) = 'higgins'; 66

及 4-10 補充  substr ( column|exp, m[,n] ) ：取子字串  從第 m 位回傳 n 個值回來  若 m 為負值, 則從右邊開始 m 位, 但取值時, 一樣是由左到右取 n 位  若 n 值忽略, 則取從 m 位到最後 select substr('ABCDEFGH', 1,3) from dual ;  ABC select substr('ABCDEFGH', -3,3) from dual;  FGH select substr('ABCDEFGH', 5) from dual ;  少最後參數, 則取全部 EFGH  instr ( column|exp, ‘string’, [,m], [n] ) ：子字串的位置, 傳回數值  從來源字串第 m 位開始找出現第 n 次的子字串, 傳回該位置  m 和 n 的預設值為 1 select instr('ABCABC', 'A') from dual ;  1 select instr('ABCABCABC', 'A',2, 2) from dual ;  7 select instr('ABCABCABC', 'A',2, 3) from dual ;  0, 找不到第 3 個 A 從第 2 個位置開始找 找尋第 2 個 A

68 補充  CONCAT : 結合兩個參數  若要結合三個參數以上 select concat(concat('A','B'),'C') from dual ;  ABC 或 select 'A'|| 'B'||'C' from dual ;  LENGTH ：求字串長度, 傳回數值 select LENGTH('ABCDEFGH') from dual;  8  LPAD(column|exp,n,’string’)  LPAD( 來源, 補齊長度, 補齊的字串 )  左邊補齊 select LPAD('ABC',5,'*') from dual ;  **ABC  RPAD(column|exp,n,’string’)  RPAD( 來源, 補齊長度, 補齊的字串 )  右邊補齊 select RPAD('ABC',5,'*') from dual ;  ABC ** select RPAD('ABC',5,'*?') from dual ;  ABC *?

補充  TRIM (leading|trailing|both trim_char FROM trim_source)  去頭尾, 預設為 both, 亦即預設頭尾皆去掉 select TRIM( both 'A' from 'BCABA') from dual ;  BCAB select TRIM( leading 'A' from 'AAAACABA') from dual ;  CABA  REPLACE: 取代  REPLACE(text,search_string, replacement_string) select REPLACE('Black and Blue', 'Bl', 'J') from dual ;  Jack and Jue 69

Using the Character-Manipulation Functions SELECT employee_id, CONCAT(first_name, last_name) NAME, job_id, LENGTH (last_name), INSTR(last_name, 'a') "Contains 'a'?" FROM employees WHERE SUBSTR(job_id, 4) = 'REP' ;  last_nam 最後一個字母為 ‘y’ 的員工 select last_name from employees where SUBSTR(last_name, -1, 1) = 'y';

Numeric Functions  ROUND (column|exp,n):  四捨五入到指定小數位數 ( specified decimal)  若 n 省略, 則到整數位, 若 n 為負值, 則從整數位向左數 n 位  TRUNC (column|exp,n): 無條件捨去到指定小數位數  若 n 省略, 其預設值為 0  MOD(m,n): 求餘數

Numeric Functions  numeric function ：只能接受數字, 並輸出數字 SQL> select ROUND(AA, 2) from dual; select ROUND(AA, 2) from dual * ERROR at line 1: ORA-00904: "AA": invalid identifier SQL> select ROUND('AA', 2) from dual; select ROUND('AA', 2) from dual * ERROR at line 1: ORA-01722: invalid number

Using the ROUND Function  DUAL  一個 public table 用以查詢 functions and calculations 結果 (view results)  dual 為 SYS 擁有, 可以給所有使用者使用, 包含一個欄位 DUMMY, 一列值為 X  round : 除了數字也可用於 date function SELECT ROUND(45.923,2), ROUND(45.923,0),ROUND(45.923,-1) FROM DUAL;

 trunc : 也可用於 date function SELECT TRUNC(45.923,2), TRUNC(45.923), TRUNC(45.923,-1) FROM DUAL; Using the TRUNC Function  mod  常用於決定奇, 偶數  mod 是 oracle 的 hash function SELECT last_name, salary, MOD(salary, 5000) FROM employees WHERE job_id = 'SA_REP'; 4-19 Using the MOD Function

Working with Dates  dates ：  Oracle Database stores dates in an internal numeric format: century, year, month, day, hours, minutes, and seconds  預設日期格式為 DD-MON-RR  有效日期 (Valid Oracle dates )  between January 1, 4712 B.C., and December 31, 9999 A.D. SELECT last_name, hire_date FROM employees WHERE hire_date < '01-FEB-88' ; select sysdate from dual; SELECT last_name,hire_date FROM employees WHERE hire_date = '07-6 月 -02'; 不是有效的月份

Working with Dates alter session set nls_date_format ='YYYY-MM-DD:HH24:MI:SS'; alter session set nls_date_format ='DD-MON-RR'; alter session set nls_date_language =french alter session set nls_date_language =american SQL> select sysdate from dual; SYSDATE 月 -13

RR Date Format  RR :  類似 YY, RR 可以指明不同的世紀 (centuries)

Using the SYSDATE Function  sysdate  顯示資料庫所在地點的時間 select sysdate from dual;  current_date  顯示該 session time zone 的時間 select current_date from dual; 4-25  database 將 date 儲存成數字

Using Arithmetic Operators with Dates SELECT last_name, (SYSDATE-hire_date)/7 AS WEEKS FROM employees WHERE department_id = 90;

Date-Manipulation Functions  months_between(date1,date2)  兩個日期間的月份數, 回傳值可為正或負  若 date1 > date 2, 則回傳正值  add_months(date,n)  日期加上 n  n 需為整數字且可為負值  last_day 當月最後一天  next_day (date,'char')  下一個指定日 ( 星期幾 ) 的日期  如下週一的日期 next_day(sysdate,' 星期一 ')  char 可為字串或數字, 若 char 為數字, 在 America 1 代表 Sunday

Using Date Functions select MONTHS_BETWEEN('01-9 月 -95','11-1 月 -94') from dual;  select MONTHS_BETWEEN('11-1 月 -94','01-9 月 -95') from dual;  select ADD_MONTHS ('31-1 月 -96',1) from dual;  '29-2 月 -96' select ADD_MONTHS ('31-1 月 -96',-1) from dual;  '31-12 月 -95' select NEXT_DAY ('01-9 月 -95',' 星期五 ') from dual;  '08-9 月 -95' select LAST_DAY ('01-2 月 -95') from dual;  '28-2 月 -95'

補充 :118. a monthly bonus of $50 to all the employees who have completed five years in the company. SELECT last_name, department_id, salary+50*12 "Annual Compensation" FROM employees WHERE MONTHS_BETWEEN(SYSDATE, hire_date)/12 >= 5; When you execute the statement, the "Annual Compensation" is not computed correctly. What changes would you make to the query to calculate the annual compensation correctly? A. Change the SELECT clause to SELECT last_name, department_id, salary*12+50 "Annual Compensation". B. Change the SELECT clause to SELECT last_name, department_id, salary+(50*12) "Annual Compensation". C. Change the SELECT clause to SELECT last_name, department_id, (salary+50)*12 "Annual Compensation". D. Change the SELECT clause to SELECT last_name, department_id, (salary*12)+50 "Annual Compensation". Answer: C 83 題庫 118 對於來公司滿 5 年的員工, 要給他每個月 50 元的 獎金 ; 查詢的欄位有 last_name, department_id 和 Annual Compensation ( 年薪 ) 執行時 Annual Compensation ( 年薪 ) 計算不正確, 如何修正 ?

Using Date Functions SELECT employee_id, hire_date, MONTHS_BETWEEN (SYSDATE, hire_date) TENURE, ADD_MONTHS (hire_date, 6) REVIEW, NEXT_DAY (hire_date,'FRIDAY'), LAST_DAY(hire_date) FROM employees WHERE MONTHS_BETWEEN (SYSDATE, hire_date) < 150 ;

補充 :30. SELECT first_name, employee_id, NEXT_DAY(ADD_MONTHS (hire_date, 6), 1) "Review" FROM employees; The review date is the first Monday after the completion of six months of the hiring. The NLS_TERRITORY parameter is set to AMERICA in the session. Which statement is true regarding this query? A. The query would execute to give the desired output. B. The query would not execute because date functions cannot be nested. C. The query would execute but the output would give review dates that are Sundays. D. The query would not execute because the NEXT_DAY function accepts a string as argument. Answer: C 85 題庫 30 查詢員工受雇滿 6 個月後的第一個星期一, 使用美國日期格式, 注意 : 美國每星期的第一天是星期日

Using ROUND and TRUNC Functions with Dates  round(date,'fmt')  以 fmt 格式來做四捨五入  若 fmt 為 month, 則 day( 日 ) >=16 進位到下個月的 1 日, <=15 為當 月的 1 日  若 fmt 為 year, 則 month( 月份 ) 為 1~6 月為當年 1 月 1 日, 7~12 月為下 一年的 1 月 1 日  若 fmt 省略, 則為 day

Using ROUND and TRUNC Functions with Dates SELECT employee_id, hire_date, ROUND(hire_date, 'MONTH'), TRUNC(hire_date, 'MONTH') FROM employees WHERE hire_date LIKE '%03' ;

Quiz  Which four of the following statements are true about single-row functions? a. Manipulate data items b. Accept arguments and return one value per argument c. Act on each row that is returned d. Return one result per set of rows e. May not modify the data type f. Can be nested g. Accept arguments that can be a column or an expression

補充 :86. Which three statements are true regarding single-row functions? (Choose three.) A. They can accept only one argument. B. They can be nested up to only two levels. C. They can return multiple values of more than one data type. D. They can be used in SELECT, WHERE, and ORDER BY clauses. E. They return data type can be different from the data type of the argument that is referenced. F. They can accept a column name, expression, variable name, or a user-supplied constant as arguments. Answer: D E F 89 題庫 86 可接受不只一個參數, 如 : months_between(date1,date2) 可以巢狀不只二層 回傳的值只能一個且只能為一種資料型態 參數資料型態不一樣, 回傳的資料型態也會不一樣, 如 : round(date,‘fmt’)  回傳日期的資料型態 round(45.923,2)  回傳數字的資料型態