Question: How can I create a table from another table without copying any values from the old table? Answer: To do this, the basic syntax is: CREATE TABLE new_table AS (SELECT * FROM old_table WHERE 1=2); For example: CREATE TABLE suppliers AS (SELECT * FROM companies WHERE 1=2);...
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select *,col1*col2 as new_col from table #最后会把前两列的乘积作为第三列 Remark:2. select后面跟常数or字符时产生全为该常数or字符的列 select id,label,1,"A" from ex1 id label 1 A 1 A 1 A 2 B 1 A 3 C 1 A #as可以给常数or字符的列命名 select id,label,1 as status,"A" as ...
图2-6-3 4.Find all employees in department 10 that have a job that is the same as anyone in the Sales department 语句: select * from emp2017303010 where deptno=10 and job = (select job from dep2017303010 where dname = 'SALES');; 结果(图2-6-4): 图2-6-4 7.Find all the employ...
CREATE TABLE Using Another TableA copy of an existing table can also be created using CREATE TABLE.The following SQL creates a new table called "TestTables" (which is a copy of the "Customers" table): Example CREATE TABLE TestTable ASSELECT customername, contactnameFROM customers; Try it ...
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; ...
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 constraints...
SQL查询语句大全集锦一、 简单查询简单的Transact-SQL查询只包括选择列表、FROM子句和WHERE子句。它们分别说明所查询列、查询的表或视图、以及搜索条件等。例如,下面的语句查询testtable表中姓名为“张三”的nickname字段和email字段。代码:SELECT `nickna
CREATE EXTERNAL TABLE AS SELECT (CETAS) creates an external table and then exports, in parallel, the results of a T-SQL SELECT statement.
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; ...