Ingxelo yeTafile ye-SQL

Ingxelo ye-ALTER TABLE kwi-SQL isetyenziselwa ukongeza, ukulungisa okanye ukucima iikholamu zetafile.

Sinokuphinda sisebenzise ALTER TABLE statement ukongeza okanye ukulahla iingxaki ezahlukeneyo zetafile.



I-SQL ALTER TABLE-Yongeza ikholamu entsha

Ukongeza ikholamu entsha kwitafile esele sisebenzisa is syntax:


ALTER TABLE table_name ADD column_name datatype;

Umzekelo

Le khowudi ilandelayo yongeza ikholamu 'Start_Date' kwitafile 'Abasebenzi':

ALTER TABLE Employees ADD Start_Date date;

I-SQL ALTER TABLE-Susa ikholamu

Ukususa ikholamu kwitafile ekhoyo sisebenzisa is syntax:


ALTER TABLE table_name DROP COLUMN column_name;

Umzekelo

Le khowudi ilandelayo isusa ikholamu 'Start_Date' kwitafile 'Abasebenzi':

ALTER TABLE Employees DROP COLUMN Start_Date;

I-SQL ALTER TABLE-Guqula ikholamu

Singasebenzisa ALTER TABLE ingxelo yokuguqula uhlobo lweenkcukacha zekholamu usebenzisa is syntax:

ALTER TABLE table_name MODIFY column_name datatype;

Umzekelo

Le khowudi ilandelayo itshintsha uhlobo lwedatha lwekholamu 'Start_Date' ukusuka date ukuya year:

ALTER TABLE Employees MODIFY Start_Date year;

I-SQL ALTER TABLE-Isiseko sedatha

Masithi sinetafile ebizwa ngokuba 'ngabasebenzi' kwezi kholamu zilandelayo:


+------------+-----------+----------+ | EmployeeID | FirstName | LastName | +------------+-----------+----------+ | 1

| Mark
| Otto
| | 2

| Jacob
| Thornton | | 3

| Su
| Bird
| | 4

| Sam
| Burger | +------------+-----------+----------+

Yongeza ikholamu

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 |

| +------------+-----------+----------+------------+

Guqula ikholamu

Emva koko sifuna ukuguqula uhlobo lwedatha lwekholamu 'Start_Date' ukusuka date ukuya year:

ALTER TABLE Employees MODIFY Start_Date year;

Cima ikholamu

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 | +------------+-----------+----------+