SQL - ?????? ?? ?????
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SQL - ?????? ?? ?????
- 1. ??????? ?? ?????.? ???????:? ?- ? ¨C N??? ???? ??? ???? ????? ?????? ??? ??? ????? ?? ??????.? ????? (? )domain???? ????? ?????? ??????? ???? ????? ??????, ????? ?Di?? ?-? ?- ? ¨C N??? ????? ???? ?? ??, ???? ?????? (? )V1,V2,¡Vn????? ?.Vi€Di?? ???????:? ?????? ¨C ?( ¦Ò - SELECT????? ? ¨C ? WHERE?? ¨C ?)SQL?? ?-? ???????? ???: (?¦Ò column=value )table_name?? ??????: (?( ¦Ò branch_name="Aviv" )borrow?????? ?? ?????? ??? ?? ????? ????)? ????? ¨C ?( ? ¨C Project????? ? ¨C ? SELECT?? ¨C ?.)SQL?? ?-? ???????? ???: (?( ? column1,¡,ColumnN )table_name?????? ??????? ?????????)? ??????: ))?( ? customer-name (¦Ò branch_name="Aviv"(borrow?????? ???? ?? ??????? ???? ???? ??????? ????).? ?????? ¨C ?( ? ¨C Union????? ?????? ? ¨C ?.)SQL?? ?-? ?????? ? ¨C ? ,SQL??? ????? ??????? ????? ??? ?????? ???????? ????. ????? ??? ????? ?????? ??????. ?????:? ?))?)¦Ò branch_name="Aviv" (deposit)) ? )¦Ò branch_name="Aviv" (borrow?? ?#? ?*? ?????? ?????? ¨C ?X - Cartesian Product?? ?-? ?1? ??a?? ?????? 2 ????? ?????? ??? ?? ?? ? ¨C N??? ???? 1 ?????? ?? ? ? ¨C N??? ????? ????.? ?1? ?*? ??b?? ??a?? ?#? ?????? ¨C ?( ? ¨C Intersection????? ?????? ? ¨C ?)SQL?? ?-? ?1? ?= ?c?? ??b?? ?1 ?X?? ?????? ? ¨C ? ,SQL??? ????? ??????? ????? ??? ?????? ???????? ????.? ?2? ??a?? ?2? ??c?? ?????? ??? ????? ?????? ????? ??? 2 ?????? ????? ???? ?????? ????.? ?2? ??b?? ?2? ??c?? ????? - ?¨C - Difference?? ?-? ??? ????? ?????? ????? ??? ?????? ???????? ????.? ????? ??? ???? ???? ??? ???? ??????,? ????? ????? ?????? ?????? ????? ?' ????? ??????? ????? ?'.? ?(???? ? ¨C ? Inner join?? ¨C ?)SQL?? ?????? ???? ¨C?? - Natural Join?? ?-? ?????? ???? ????? ???? ?? ????? ??? ?????? ??? 2 ??????.? ?1?R2 ? R??