1.TOP
SQL Server的語法:
SELECT TOP number columnName
FROM tableName
MySQL的語法:
SELECT columnName
FROM tableName
LIMIT number
Oracle的語法:
SELECT columnName
FROM tableName
WHERE ROWNUM<=number
2.創建表時添加UNIQUE/PRIMARY KEY/FOREIGN KEY/CHECK(不需名爲約束人爲命時纔有不兼容)
(接下來舉例說明)
SQL Server/Oracle/Access的語法:
CREATE TABLE Students
(Name char(10) NOT NULL,
Id char(10) NOT NULL UNIQUE
)
MySQL的語法:
CREATE TABLE Students
(Name char(10) NOT NULL,
Id char(10) NOT NULL,
UNIQUE(Id)
)
PRIMARY KEY和UNIQUE同理,只是把UNIQUE換成PRIMARY KEY而已;
FOREIGN KEY也是同理,只不過要加上REFERENCES的內容而已;
CHECK也是同理,只不過要加上約束的內容而已;
3.撤銷UNIQUE
SQL Server/Oracle/Access的語法:
ALTER TABLE TableName
DROP CONSTRAINT constraintName
MySQL的語法:
ALTER TABLE TableName
DROP INDEX indexName
4.撤銷PRIMARY KEY
SQL Server/Oracle/Access的語法:
ALTER TABLE TableName
DROP CONSTRAINT constraintName
MySQL的語法:
ALTER TABLE TableName
DROP PRIMARY KEY
5.撤銷FOREIGN KEYSQL Server/Oracle/Access的語法:
ALTER TABLE TableName
DROP CONSTRAINT constraintName
MySQL的語法:
ALTER TABLE TableName
DROP FOREIGN KEY foreignKeyName
SQL Server/Oracle/Access的語法:
ALTER TABLE TableName
DROP CONSTRAINT constraintName
MySQL的語法:
ALTER TABLE TableName
DROP CHECK checkName7.爲已有的表添加DEFAULT
SQL Server/Oracle/Access的語法:
ALTER TABLE tableName
ALTER columnName SET DEFAULT 'defaultValue'
MySQL的語法:
ALTER TABLE tableName
ALTER COLUMN columnName SET DEFAULT 'defaultValue'
8.撤銷DEFAULT
SQL Server/Oracle/Access的語法:
ALTER TABLE tableName
ALTER columnName DROP DEFAULT
MySQL的語法:
ALTER TABLE tableName
ALTER COLUMN columnName DROP DEFAULT
SQL Server的語法:
DROP INDEX tableName.columnName
Oracle的語法:
DROP INDEX indexName
Access的語法:
DROP INDEX indexName ON tableName
MySQL的語法:
ALTER TABLE tableName
DROP INDEX indexName
當然,不同的數據庫在時間處理等方面還有不同,但由於文本過長,在此不再贅述。