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¼Õº´¸ñ
(2002-05-08 15:19:01, Hit : 17937, Vote : 2244)
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Subject
DDL(Data Definition Language) - ALTER TABLE
Áö³ ½Ã°£¿¡ CREATE¸¦ ÀÌ¿ëÇØ Å×À̺íÀ» ¸¸µå´Â DDLÀ» ½Ç½ÀÇß½À´Ï´Ù.
À̹ø ½Ã°£¿¡´Â ¸¸µé¾î ³õÀº Å×À̺íÀ» º¯°æÇÏ´Â ¸í·ÉÀÎ ALTER¿¡ ´ëÇØ ½Ç½ÀÇϰڽÀ´Ï´Ù.(±×¸®°í ´ÙÀ½ ½Ã°£¿¡´Â »èÁ¦ ¸í·ÉÀÎ DROPÀ» ½Ç½ÀÇÒ ¿¹Á¤ÀÔ´Ï´Ù.)
ALTER
´Â,
±âÁ¸ Å×ÀÌºí¿¡ »õ·Î¿î Ä÷³À» Ãß°¡Çϰųª º¯°æ(Ä÷³ÀÇ µ¥ÀÌÅÍÇü º¯°æ µî)ÇÒ ¶§ ALTER ¸í·ÉÀ» »ç¿ëÇÕ´Ï´Ù.
ALTER ¸í·ÉÀº Constraint¸¦ Ãß°¡Çϰųª »èÁ¦ÇÒ ¶§µµ »ç¿ëÇÒ ¼ö ÀÖ½À´Ï´Ù.
±×·¯³ª CREATE TABLE ¹®À¸·Î ¸¸µç Ä÷³Àº »èÁ¦ÇÒ ¼ö ¾ø½À´Ï´Ù.
ALTER ¹®Àº ´ÙÀ½°ú °°ÀÌ »ç¿ëµË´Ï´Ù.
ALTER TABLE
table_name
ADD ( column_name datatype )
MODIFY( column_name datatype )
ADD CONSTRAINT constraint_name expr
DROP CONSTRAINT constraint_name;
½Ç½À 1
±âÁ¸ C_EMP Å×ÀÌºí¿¡ AGE Ä÷³À» Ãß°¡ÇÏ°í ±âÁ¸ÀÇ EMP_NAME Ä÷³ÀÇ ±æÀ̸¦ 20À¸·Î ÁÙÀ̱â.(´Ü, AGE´Â 0º¸´Ù Ä¿¾ßÇϰí, ÀÌ Á¶°ÇÀÇ À̸§À» CK_AGE¶ó°í ÇÑ´Ù.)
ALTER TABLE C_EMP
ADD (AGE NUMBER(3))
MODIFY (EMP_NAME VARCHAR(20))
ADD CONSTRAINT CK_AGE CHECK(AGE > 0);
½Ç½À 2
C_EMP Å×ÀÌºí¿¡¼ ±âÁ¸ÀÇ FK_DEPTNO¶ó´Â CONSTRAINT¸¦ »èÁ¦Çϱâ
ALTER TABLE C_EMP
DROP CONSTRAINT FK_DEPTNO;
½Ç½À 3
C_EMP Å×ÀÌºí¿¡¼ DEPT_NO Ä÷³¿¡ Foreign Key Constraint¸¦ Ãß°¡Çϱâ(´Ü, Foreign Key ConstraintÀÇ À̸§Àº FK_EMP_DEPTNO·Î ÇÑ´Ù.)
ALTER TABLE C_EMP
ADD CONSTRAINT FK_EMP_DEPTNO
FOREIGN KEY(DEPT_NO) REFERENCES DEPT;
¹®¹ýÀûÀ¸·Î ¾î·Á¿î °ÍÀº ÀüÇô ¾ø´Âµ¥ ½ÇÁ¦ ½Ç¹«¿¡¼ »ç¿ëÇÏ·Á°í Çϸé Àß ±â¾ï³ªÁö ¾ÊÀ» ¶§°¡ ÀÖ½À´Ï´Ù.
¸ðµç °ÍÀÌ ±×·¯Çϵí ÀÚÁÖ »ç¿ëÇØ¾ß ±â¾ïÇÒ ¼ö ÀÖ°ÚÁÒ.
ÀÌ»ó µ¿ÁÖ ¾Æºü ¼Õº´¸ñÀ̾ú½À´Ï´Ù.
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