foreign key field access

Tags: on as SQL type Oracle table text class ROMQuery all columns and their properties for a table:Select From User_tab_columns t,user_col_comments Cwhere t.table_name = c.table_name and T.column_name = c.column_name and t.table_name = women;To find the primary key for a table:Find the foreign key of the table (including the name, the table name of the referen

1, add a new field for the currently existing tableALTER TABLE student add studentname varchar (a) not null;2, set the primary key self-increment for the fields in the currently existing tableALTER TABLE student add constraint Pk_studentid PrimaryKey (StudentID);3, set a foreign key for the

. column_id) As Description From SYS. columns, SYS. Tables, SYS. Types Where SYS. columns. Object_id = SYS. Tables. Object_id And SYS. Columns. system_type_id = SYS. types. system_type_id And SYS. Tables. Name = @ Table_name Order By SYS. Columns. column_id Running Effect 3. Independently query incremental fields of the table -- Separately query the incremental field of the table Select [ Name ] From S

Because the data structure design of some modules of the project is not strictly in accordance with certain specifications, the data structure can only be queried from the database. The information to be queried is as follows: field name, data type, whether it is null, default value, primary key, foreign key, and so on

1. Get basic field attributes of the tableObtain Table Structure in sqlserver Select Syscolumns. Name, policypes. Name, syscolumns. isnullable, Syscolumns. Length From Syscolumns, policypes Where Syscolumns. xusertype = Policypes. xusertype And Syscolumns. ID = Object_id ( ' Your table name ' ) Running Effect 3. Independently query incremental fields of the table-- Separately query the incremental

ID int (4) is not null;mysql> ALTER TABLE DEMO5 drop PRIMARY key;Summary: Primary key index, uniqueness Index difference: Primary key index cannot have null, uniqueness index can have null valueComposite IndexAn index can contain one, two, or more columns. An index on two or more columns is called a composite index43. Federated PRIMARY

itCREATE TABLE Table name (Column definition,Fulltext Key index name (field);）Method Two: Add when modifying a tableALTER TABLE name ADD Fulltext index name (field);ALTER TABLE ' books ' ADD Fulltext Index name (' author ')Strong note: MySQL comes with a full-text index only for data tables that are MyISAM by the database engine, and if it is a different data en

Summary of index, foreign key, and field syntax maintenance for mysql, SQL Server, and oracle databases, and SQL Server oracle Summary of index, foreign key, and field syntax maintenance for mysql, SQL Server, and oracle databases

1. The type or size of the two fields does not match exactly. For example, if one is an int (10), then the foreign key must also be set to int (10), not int (11), or tinyint. In addition, you must determine whether the two fields are one signed, and the other is unsigned (i.e. unsigned), which must match exactly, more information about signed and unsigned, see:/http www.verysimple.com/blog/?p=572. The

I hope that I can clearly analyze the primary and foreign key tables and field information like SQL Server, use an SQL statement to write out the one-to-one correspondence between the fields in the primary and foreign key tables, and find them online for half a day, the prim

It was difficult to delete a foreign key without specifying a name. It is very complicated to delete it on different databases. A script is specially written to delete the foreign key on a specified field. It was difficult to delete a fo