SQL Modify Field length

Grammar:

Alter Table < table name >altercolumn< field name > new type name (length)

Example: If a named T1, the field name F1, the original F1 is varchar (3), now to varchar (10), then you can write:

Alter Table Alter column varchar (ten)

In general, you can use this statement to change the field name :

Alter Table column  to C

However, in practical applications, we tend to compile with j-sql, and J-sql does not support modifying field names, so if you must modify the field name, then only through the workaround, the specific idea is:
1. Create a new field, named C;
2. Copy the contents of field A to C;
3. Delete field A;

syntax for SQL to modify field lengths:

ALTER TABLE name modify field type;

Example code for SQL to modify field lengths

Alter Table VARCHAR2 (4000);

Standard SQL, applicable to any database

Alter Table varchar (a);

Modify Field name Name

ALTER TABLE  COLUMN  to COL2;

Add Field

Alter Table Add  Stationstate  CHAR(1)

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SQL Modify Field length