Note Candidate indexes, created by including the UNIQUE option (provided for ANSI compatibility) in CREATE TABLE – SQL or ALTER TABLE – SQL commands, are not the same as indexes created in the INDEX command with the UNIQUE option. An index created in the INDEX command using the UNIQUE opti...
Visual FoxPro uses the default value if you use the SQL ALTER TABLEcommand to remove autoincrementing for the field.PRIMARY KEY | UNIQUE PRIMARY KEY creates a primary index for the field specified in FieldName1. UNIQUE creates a candidate index for the field specified in FieldName1. The ...
Creates a table having the specified fields.The Visual FoxPro ODBC Driver supports the native Visual FoxPro language syntax for this command. For driver-specific information, see Driver Remarks.SyntaxCopy CREATE TABLE | DBF TableName1 [NAME LongTableName] [FREE] (FieldName1FieldType [(n...
Here, the SQL command checks if a table namedCompaniesexists, and if not, it creates a table with specified columns. 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 t...
CREATE TABLE TheCREATE TABLEcommand creates a new table in the database. The following SQL creates a table called "Persons" that contains five columns: PersonID, LastName, FirstName, Address, and City: Example CREATETABLEPersons ( PersonID int,...
候選索引(在 CREATE TABLE 或 ALTER TABLE - SQL 中包含 UNIQUE 選項所建立的索引,與 INDEX 命令中的 UNIQUE 選項所建立的索引不同。 在 INDEX 命令中使用 UNIQUE 選項建立的索引允許重複索引鍵;候選索引不允許重複的索引鍵。 如需 UNIQUE 選項的其他資訊,請參閱 INDEX。 在用於主要或候選索引的欄位中,不允許...
CREATE TABLE guestbook (visitor VARCHAR(40),comments TEXT,entrydate DATETIME) 如果一切正常,如果在sql企业管理器中执行以上查询,将返回 This command dit not return data ,and it did not return any rows 祝贺你,你已经建立了你的第一个表! 你所创建的表名为guestbook,你可以使用这个表来存储来字你站点访...
Createtableroom ( room_nointPRIMARYKEY, room_typevarchar(20)NOTNULL, statusvarchar(10)CHECKIN('occupied','free') ); Once we execute the above query, it shows the message of ‘table created successfully’ In the previous query of SQL create we use to check to constrain with IN command we...
command.Connection=newSqlConnection(connStr);//第三步:创建SqlDataAdapterSqlDataAdapter adapter =newSqlDataAdapter(command);//第四步:创建DataSet和DataTableDataSet dataSet =newDataSet(); DataTable dataTable=newDataTable();//第五步:填充数据adapter.Fill(dataTable); ...
通过println,输出 show create table orders 的物理执行计划,可看到,真正执行的是ShowCreateTableCommand这个类。 代码流程: 两个核心方法: 查hive元数据库(ObjectStore.getMTable) mtbl = (MTable) query.execute(table, db)对应的sql: 获取表的一些基本信息(tbl_id, tbl_type等) ...