We use the following SQL statement: ALTERTABLEPersons ALTERCOLUMNDateOfBirth year; Notice that the "DateOfBirth" column is now of type year and is going to hold a year in a two- or four-digit format. DROP COLUMN
To modify multiple columns in an existing table, the ALTER TABLE syntax is: ALTER TABLE table_name For Example: ALTER TABLE supplier This will modify both thesupplier_nameandcitycolumns. Drop column(s) in a table Syntax #1 To drop a column in an existing table, the ALTER TABLE syntax is:...
-- delete country column from Customers tableALTERTABLECustomersDROPCOLUMNcountry; Run Code Here, the SQL command removes thecountrycolumn from theCustomerstable. Rename a Table We can change the name of a table using theALTER TABLEcommand with theRENAMEclause. For example, -- rename Customers tab...
SQL ALTER TABLE StatementThe SQL ALTER TABLE command is used to modify the definition (structure) of a table by modifying the definition of its columns. The ALTER command is used to perform the following functions. 1) Add, drop, modify table columns 2) Add and drop constraints 3) ...
For existing rows, the value is that of the SESSION_USER special register at the time the ALTER TABLE statement is processed. CURRENT SQLID Specifies the value of the SQL authorization ID of the process at the time of an SQL data change statement or LOAD, as the default for the column....
CREATE TABLE employees(employee_numbernumber(10)not null, employee_namevarchar2(50)not null, department_idnumber(10), CONSTRAINT employees_pk PRIMARY KEY (employee_number)); Solution: The following ALTER TABLE statement would add asalarycolumn to theemployeestable: ...
Use the ALTER TABLE statement to alter the definition of a nonpartitioned table, a partitioned table, a table partition, or a table subpartition. For object tables or relational tables with object columns, use ALTER TABLE to convert the table to the latest definition of its referenced type ...
第二章 SQL命令 ALTER TABLE(二) 删除列限制 DROP COLUMN可以删除指定为逗号分隔列表的多个列定义。每个列出的列名后面必须紧跟其RESTORY或CASCADE(如果未指定,则默认为RESTRICE)和%DELDATA或%NODELDATE(如果未指定,则默认为%NODELDATA)选项。 默认情况下,删除列定义不会从数据映射中删除存储在该列中的任何数据。
This is a MySQL extension to standard SQL, which permits only one of each clause per ALTER TABLE statement. For example, to drop multiple columns in a single statement, do this: ALTER TABLE t2 DROP COLUMN c, DROP COLUMN d; If a storage engine does not support an attempted ALTER TABLE...
the following SQL statement can be used: SQL Code: ALTER TABLE agent1 -- Modify the default value of the column 'commission' in the table 'agent1' MODIFY commission DEFAULT .05; Explanation: ALTER TABLE agent1: Begins the SQL statement to alter the structure of the existing table named '...