sql alter table not null constraint

, and now I want to modify it through the SQL statement, what can I do to change it, please tell the friend in detail ALTER TABLE [table name] ALTER COLUMN [column name] data type (length) not null such as:

I found a problem when I was studying the database today. The prompt is as follows:The alter table statement conflicts with the foreign key constraint "fk_student_parents_id_parents_id. This conflict occurs in the Database "school", table "DBO. Parents", column 'id '.I still need to paste my two tables into a graph:Thi

Common SQL change and query statements Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->Select *, (case when type = 1 then (Select typename from tableatype where type = 1) When type = 2 then (Select typename from tableatype where type = 2) When type = 3 then (Select typename from tableatype where type = 3) Else (Select typename from tableatype where type = 4) End ) As typetmp from tablea =============

Before testing and use of the time really did not find this problem, always think that copy_table_dependents will automatically filter not NULL constraints. However, the fact is that, if you intend to use the Copy_table_dependents procedure to replicate related objects such as indexes, constraints, and permissions, the existence of a NOT NULL constraint raises a

ALTER TABLE Parse instance: sql:1. Add columns 2. Add columns, adjust column order 3. Increase the index 4. Increase the constraint 5. Increase the full-text index FULL-TEXT6. Change the default value of the column 7. Change the column name (type, order) 8. Do not change the column name 9. Delete Column 10. Delete the

; This will drop the Supplier_name table column named vendor. Rename column in table (S)(New in Oracle 9i 2nd edition)Grammar # At the beginning of the 2nd edition of Oracle9i, you can now rename the columns. To rename a column in an existing table, the syntax of ALTER

' auc_attention ' MODIFY COLUMN ' auc_id ' varchar (255) null DEFAULT NULL after ' ID '; --Auc_brand_no_generator ALTER TABLE ' auc_brand_no_generator ' MODIFY COLUMN ' auc_id ' varchar (255) null DEFAULT null A fter ' id '; --

' auc_attention ' MODIFY COLUMN ' auc_id ' varchar (255) null DEFAULT NULL after ' ID '; --Auc_brand_no_generator ALTER TABLE ' auc_brand_no_generator ' MODIFY COLUMN ' auc_id ' varchar (255) null DEFAULT null A fter ' id '; --

* from sysobjects where name = ' Grade ') drop table Grade Use School Go ---Create a grande grade table-- Copy Code code as follows: CREATE TABLE Grade ( Gradeid int NOT NULL, Grandename nvarchar (50) ) -----------------------------------------t-

SQL statement set of The alter TABLE in mysql, including adding, modifying, and deleting fields, renaming tables, and adding and deleting primary keys. This article introduces the SQL statement set of the alter table of the MySql

foreign key are updated to the new value specified for this key. (If the timestamp column is a foreign key or a part of the referenced key, cascade cannot be specified. )On Delete set nullSpecify that if you try to delete a row, and the row's key is referenced by the foreign key in the existing row of another table, all values that constitute the foreign key in the referenced row will be set to null. All f

ConstraintName? 1 ALTER TABLE student DROP CONSTRAINT PK__student__2F36BC5B772B9A0B 10. Adding field constraints Format: ALTER TABLE tablename ADD constraint ConstraintName primary key (column_nam

constraint UQ _stuno, delete if EXISTS (SELECT * from sysobjects WHERE name= ' uq_stuid ' and xtype= ' UQ ') Alter TABLE stuinfodrop Constraint U q_stuidgo--add unique constraint uq_stuidalter TABLE stuinfo add

can replace us in finding and solving many problems ). The Code is as follows: SelectFk. name, fk. object_id, OBJECT_NAME (fk. parent_object_id) as referenceTableNameFrom sys. foreign_keys as fkJoin sys. objects as o on fk. referenced_object_id = o. object_idWhere o. name = 'referenced table name' The preceding SQL statement can obtain the foreign key references to a

xtype= ' PK ') Alter TABLE stuinfo Drop Constraint Pk_stuno Go--Re-add PRIMARY KEY constraint Pk_stuno ALTER TABLE stuinfo add CONSTRAINT pk_stuno PRIMARY key (Stuno) Go--Example 3 add