資料庫_函式_資料準備
阿新 • • 發佈：2018-11-10
SQL中可供使用的函式是非常多的，這些函式的功能包括轉換字串大小寫、求一個數的對數、計算兩個日期之間的天數間隔等，數量的掌握這些函式將能夠幫助我們更快的完成業務功能。本章將講解這些函式的使用，並且對它們在不同資料庫系統中的差異性進行比較。為了更容易的執行本章中的例子，必須首先建立所需要的資料表，因此下面列出用到資料表的建立SQL語句：
MYSQL:
CREATE TABLE T_Person (FIdNumber VARCHAR(20),FName VARCHAR(20),FBirthDay DATETIME,FRegDay DATETIME,FWeight DECIMAL(10,2)) MSSQLServer: CREATE TABLE T_Person (FIdNumber VARCHAR(20),FName VARCHAR(20),FBirthDay DATETIME,FRegDay DATETIME,FWeight NUMERIC(10,2)) Oracle: CREATE TABLE T_Person (FIdNumber VARCHAR2(20),FName VARCHAR2(20),FBirthDay DATE,FRegDay DATE,FWeight NUMERIC(10,2)) DB2: CREATE TABLE T_Person (FIdNumber VARCHAR(20),FName VARCHAR(20),FBirthDay DATE, 請在不同的資料庫系統中執行相應的SQL 語句。T_Person為記錄人員資訊的資料表，其中欄位FIdNumber 為人員的身份證號碼，FName 為人員姓名，FBirthDay 為出生日期，FRegDay為註冊日期，FWeight為體重。
為了更加直觀的驗證本章中函式使用方法的正確性，我們需要在T_Person 表中預置一些初始資料，請在資料庫中執行下面的資料插入SQL語句：
MYSQL、MSSQLServer、DB2：
INSERT INTO T_Person(FIdNumber,FName,FBirthDay,FRegDay,FWeight) VALUES ("123456789120","Tom","1981-03-22","1998-05-01",56.67); INSERT INTO T_Person(FIdNumber,FName,FBirthDay,FRegDay,FWeight) VALUES ("123456789121","Jim","1987-01-18","1999-08-21",36.17); INSERT INTO T_Person(FIdNumber,FName,FBirthDay,FRegDay,FWeight) VALUES ("123456789122","Lily","1987-11-08","2001-09-18",40.33); INSERT INTO T_Person(FIdNumber,FName,FBirthDay,FRegDay,FWeight) VALUES ("123456789123","Kelly","1982-07-12","2000-03-01",46.23); INSERT INTO T_Person(FIdNumber,FName,FBirthDay,FRegDay,FWeight) VALUES ("123456789124","Sam","1983-02-16","1998-05-01",48.68); INSERT INTO T_Person(FIdNumber,FName,FBirthDay,FRegDay,FWeight) VALUES ("123456789125","Kerry","1984-08-07","1999-03-01",66.67); INSERT INTO T_Person(FIdNumber,FName,FBirthDay,FRegDay,FWeight) VALUES ("123456789126","Smith","1980-01-09","2002-09-23",51.28); INSERT INTO T_Person(FIdNumber,FName,FBirthDay,FRegDay,FWeight) VALUES("123456789127","BillGates","1972-07-18","1995-06-19",60.32); Oracle： INSERT INTO T_Person(FIdNumber,FName,FBirthDay,FRegDay,FWeight) VALUES ("123456789120","Tom",TO_DATE("1981-03-22", "YYYY-MM-DD HH24:MI:SS"),TO_DATE("1998-05-01", "YYYY-MM-DD HH24:MI:SS"),56.67); INSERT INTO T_Person(FIdNumber,FName,FBirthDay,FRegDay,FWeight) VALUES ("123456789121","Jim",TO_DATE("1987-01-18", "YYYY-MM-DD HH24:MI:SS"),TO_DATE("1999-08-21", "YYYY-MM-DD HH24:MI:SS"),36.17); INSERT INTO T_Person(FIdNumber,FName,FBirthDay,FRegDay,FWeight) VALUES ("123456789122","Lily",TO_DATE("1987-11-08", "YYYY-MM-DD HH24:MI:SS"),TO_DATE("2001-09-18", "YYYY-MM-DD HH24:MI:SS"),40.33); INSERT INTO T_Person(FIdNumber,FName,FBirthDay,FRegDay,FWeight) VALUES ("123456789123","Kelly",TO_DATE("1982-07-12", "YYYY-MM-DD HH24:MI:SS"),TO_DATE("2000-03-01", "YYYY-MM-DD HH24:MI:SS"),46.23); INSERT INTO T_Person(FIdNumber,FName,FBirthDay,FRegDay,FWeight) VALUES ("123456789124","Sam",TO_DATE("1983-02-16", "YYYY-MM-DD HH24:MI:SS"),TO_DATE("1998-05-01", "YYYY-MM-DD HH24:MI:SS"),48.68); INSERT INTO T_Person(FIdNumber,FName,FBirthDay,FRegDay,FWeight) VALUES ("123456789125","Kerry",TO_DATE("1984-08-07", "YYYY-MM-DD HH24:MI:SS"),TO_DATE("1999-03-01", "YYYY-MM-DD HH24:MI:SS"),66.67); INSERT INTO T_Person(FIdNumber,FName,FBirthDay,FRegDay,FWeight) VALUES ("123456789126","Smith",TO_DATE("1980-01-09", "YYYY-MM-DD HH24:MI:SS"),TO_DATE("2002-09-23", "YYYY-MM-DD HH24:MI:SS"),51.28); INSERT INTO T_Person(FIdNumber,FName,FBirthDay,FRegDay,FWeight) VALUES ("123456789127","BillGates",TO_DATE("1972-07-18", "YYYY-MM-DD HH24:MI:SS"),TO_DATE("1995-06-19", "YYYY-MM-DD HH24:MI:SS"),60.32); 初始資料預置完畢以後執行SELECT * FROM T_Person來查看錶中的資料。