The ALTER TABLE.. ADD COLUMN statement adds a column to an existing table. This operation is online in TiDB, which means that neither reads or writes to the table are blocked by adding a column ...

Adds columns to, drops columns from, and changes column attributes in an existing table. Adds, modifies, and drops integrity constraints from an existing table. Restriction: You cannot use any type of ...

Specifies whether the column can accept NULL values. Columns that do not allow NULL values can be added only if they have a default specified. If the new column allows NULL values and no default is ...

How to Create a Table From Query Results in Microsoft SQL. If your business uses relational databases to store data, you may have used a SQL SELECT clause to create new tables from query results.