Ingxelo ye-ALTER TABLE kwi-SQL isetyenziselwa ukongeza, ukulungisa okanye ukucima iikholamu zetafile.
Sinokuphinda sisebenzise ALTER TABLE statement ukongeza okanye ukulahla iingxaki ezahlukeneyo zetafile.
Ukongeza ikholamu entsha kwitafile esele sisebenzisa is syntax:
ALTER TABLE table_name ADD column_name datatype;
Le khowudi ilandelayo yongeza ikholamu 'Start_Date' kwitafile 'Abasebenzi':
ALTER TABLE Employees ADD Start_Date date;
Ukususa ikholamu kwitafile ekhoyo sisebenzisa is syntax:
ALTER TABLE table_name DROP COLUMN column_name;
Le khowudi ilandelayo isusa ikholamu 'Start_Date' kwitafile 'Abasebenzi':
ALTER TABLE Employees DROP COLUMN Start_Date;
Singasebenzisa ALTER TABLE
ingxelo yokuguqula uhlobo lweenkcukacha zekholamu usebenzisa is syntax:
ALTER TABLE table_name MODIFY column_name datatype;
Le khowudi ilandelayo itshintsha uhlobo lwedatha lwekholamu 'Start_Date' ukusuka date
ukuya year
:
ALTER TABLE Employees MODIFY Start_Date year;
Masithi sinetafile ebizwa ngokuba 'ngabasebenzi' kwezi kholamu zilandelayo:
+------------+-----------+----------+ | EmployeeID | FirstName | LastName | +------------+-----------+----------+ | 1
| Mark
| Otto
| | 2
| Jacob
| Thornton | | 3
| Su
| Bird
| | 4
| Sam
| Burger | +------------+-----------+----------+
Ngoku sifuna ukwandisa itafile 'Abasebenzi' kwaye sidibanise ikholamu entsha ebizwa ngokuba yi 'Start_Date'
ALTER TABLE Employees ADD Start_Date date;
Iziphumo:
+------------+-----------+----------+------------+ | EmployeeID | FirstName | LastName | Start_Date | +------------+-----------+----------+------------+ | 1
| Mark
| Otto
|
| | 2
| Jacob
| Thornton |
| | 3
| Su
| Bird
|
| | 4
| Sam
| Burger |
| +------------+-----------+----------+------------+
Emva koko sifuna ukuguqula uhlobo lwedatha lwekholamu 'Start_Date' ukusuka date
ukuya year
:
ALTER TABLE Employees MODIFY Start_Date year;
Sifuna ukucima ikholamu ye 'Start_Date' kwiitafile zabasebenzi. Sisebenzisa:
ALTER TABLE Employees DROP COLUMN Start_Date;
Iziphumo:
+------------+-----------+----------+ | EmployeeID | FirstName | LastName | +------------+-----------+----------+ | 1
| Mark
| Otto
| | 2
| Jacob
| Thornton | | 3
| Su
| Bird
| | 4
| Sam
| Burger | +------------+-----------+----------+