It is important to note that when creating a table in this way, the new table will be populated with the records from the existing table (based on the SELECT Statement). Syntax #1 - Copying all columns from another table The basic syntax is: CREATE TABLE new_table AS (SELECT * FROM ol...
The following example shows how to reference this key from another table; an explicit constraint name is optional. SQL Copy CONSTRAINT FK_SpecialOfferProduct_SalesOrderDetail FOREIGN KEY (ProductID, SpecialOfferID) REFERENCES SpecialOfferProduct (ProductID, SpecialOfferID) C. Use UNIQUE constrai...
[code]INSERT anothertable(another_first,another_second) VALUES(@@identity,’some value’) 如果表mytable有一个标识字段,该字段的值会被插入表anothertable的another_first字段。这是因为变量@@identity总是保存最后一次插入标识字段的值。 字段another_first应该与字段first_column有相同的数据类型。但是,字段another...
-- Creates a Delta table>CREATETABLEstudent (idINT,nameSTRING, ageINT);-- Use data from another table>CREATETABLEstudent_copyASSELECT*FROMstudent;-- Creates a CSV table from an external directory>CREATETABLEstudentUSINGCSV LOCATION'/path/to/csv_files';-- Specify table comment and proper...
CREATE TABLE Using Another TableThe following SQL creates a new table called "TestTables" (which is a copy of two columns of the "Customers" table): Example CREATE TABLE TestTable ASSELECT customername, contactnameFROM customers; ❮ Previous ❮ SQL Keywords Reference Next ❯ ...
Create Table Using Another Existing Table In SQL, we can create a new table by duplicating an existing table's structure. Let's look at an example. -- create a backup table from the existing table CustomersCREATETABLECustomersBackupASSELECT*FROMCustomers; ...
相应的,也可以drop table 可以drop View 可以drop Index 可以drop trigger/procedure delete 用于删除行数据 语法规则:drop 对象 对象名 删除某一个属性,alter table 表名 drop column 属性名; 更改操作:用于更新数据,使用update命令 查找数据:使用select - from - where范式进行查找 ...
CREATETABLEbookshelf(BOOK_IDNUMBER,BOOK_NAMEVARCHAR2(100),BOOK_TYPEVARCHAR2(100),AUTHORVARCHAR2(100),INTIMEDATE); 表名为:bookshelf,有列:图书id,图书名称,图书类型,作者,入库时间。通过上面学习的SELECT语法,来查询一下这张表: SELECT * FROM bookshelf; ...
CREATE TABLE Using Another Table A copy of an existing table can also be created usingCREATE TABLE. The following SQL creates a new table called "TestTables" (which is a copy of the "Customers" table): Example CREATETABLETestTableAS
例如: 表 TAB1 16,384 条记录表 TAB2 5 条记录,选择TAB2作为基础表 (最好的方法) select count(*) from tab1,tab2 执行时间0.96秒,选择TAB2作为基础表 (不佳的方法) select count(*) from tab2,tab1 执行时间26.09秒; 如果有3个以上的表连接查询,那就需要选择交叉表(intersection table)作为基础表,...