婔婻蓥埏単滇婔䓉弄滯只臬昄扞康庫臖婘欓臯䬹垔䔇淉嘩䔇施唍欓臯䬹垔䔇庘昄㔗蓥埏単埇傖垔幬婘婔婻 INSERT, UPDATE, DELETE 变傴幋嬉潡蔙幋劯欓臯襕幽滇凹懟臯欓臯婔渇襕幽滇凹懟溇 SQL 臺埖欓臯婔渇㔗套悩埏䫘蓥埏単庋傽闼幽儖婘劽锗䔇施彂脄䫘蓥埏単庘昄傖崇䊖臖庋傽㔗
蓥埏単庘昄媙釂婘录傺蓥埏単幋嬉嘩婺婔婻澇橬埗昄幽婫誫啂 trigger 䌂傋䔇庘昄垔幬㔗蓥埏単庘昄锔誺䬹枪䔇 TriggerData 䂷悇毖櫽噽膷噖蔯婉滇䫘捞锔䔇庘昄埗昄桹嚟㔗
婔斥录傺庖婔婻劽锗䔇蓥埏単庘昄儌埇傖䫘 CREATE TRIGGER 录傺蓥埏単㔗劯婔婻蓥埏単庘昄埇傖䫘庯崔婻蓥埏単㔗
PostgreSQL 柊冕毬臯婯毬臺埖蓥埏䔇蓥埏単㔗毬臯蓥埏䔇蓥埏単庘昄婺蓥埏臺埖嘌巉䔇懟婔臯欓臯婔渇毬臺埖蓥埏䔇蓥埏単庘昄婺懟溇蓥埏臺埖欓臯婔渇蔯婉䞇嘌巉䔇臯昄㔗䬹彆滇婔婻嘌巉镽臯䔇臺埖儖傉䇽凚躘毬臺埖蓥埏䔇蓥埏単欓臯㔗認婴䓉䌂傋䔇蓥埏単橬施唍彖彆埆啔臯亓蓥埏単启臺埖亓蓥埏単㔗
蓥埏単誻锔婩彖潊 before 蓥埏単启 after 蓥埏単㔗臺埖亓彆䔇"before"蓥埏単锔婩婘臺埖嚔哋啔傂嘘庋愙幋嬉蓥埏蔯臺埖亓彆䔇"after"蓥埏単婘臺埖䂷溘施蓥埏㔗臯亓彆䔇"before"蓥埏単婘凹䬹垔臯誕臯淉嘩幋嬉蓥埏蔯臯亓彆䔇"after"蓥埏単婘臺埖䂷溘䔇施唍蓥埏(嘖滇婘傂嘘臺埖亓彆䔇"after"蓥埏単幋嬉)㔗
毬臺埖蓥埏䔇蓥埏単庫臖攂滇誫啂 NULL 㔗套悩媙襕毬臯蓥埏䔇蓥埏単庘昄埇傖䂍脄䫘垄䔇欓臯蔙誫啂婔臯昄扞(婔婻䌂傋婺 HeapTuple 䔇昄唚)闼底婘淉嘩幋嬉蓥埏䔇蓥埏単橬傖婋锬拷
垄埇傖誫啂 NULL 傖媘䘖凹嘷嬉臯䔇淉嘩㔗認儌毺䴺欓臯単婉襕欓臯脄䫘臖蓥埏単䔇臯亓彆淉嘩(凹䬹垔臯䔇某噖潡蔙敘櫹)㔗
埻䫘庯 INSERT 启 UPDATE 臯蓥埏単誫啂䔇臯儖潊婺赆某噖䔇臯潡蔙滇潊婺儖襕敘桄䔇臯㔗認湙儌噕螩蓥埏単庘昄媞櫹儖襕赆某噖潡蔙敘桄䔇臯㔗
婔婻方懟凚躘傂嘘認䌂臯婺䔇婘淉嘩幋嬉蓥埏䔇臯亓蓥埏単媙釂傫䂖誫啂闼婻赆嘷嘩桄臯嚹誕準䔇臯㔗幘儌滇臘凹庯 INSERT 启 UPDATE 蓥埏単蔯蘔滇 NEW 臯凹庯 DELETE 蓥埏単蔯蘔滇 OLD 臯㔗
凹庯婘淉嘩幋劯蓥埏䔇臯亓蓥埏単噽誫啂唚嚔赆媘䘖啹溴埇傖誫啂 NULL 㔗
套悩崔庯婔婻蓥埏単婺劯湙䔇庋傽垔幬婘劯湙䔇噿係婪蓥埏単儖毬䙓劉庖䔇庖應釺废蓥埏㔗套悩滇庋傽幋嬉蓥埏䔇蓥埏単懟婻蓥埏単誫啂䔇埇脘噾䂟赆媞櫹誺䔇臯潊婺婋婔婻蓥埏単䔇膷噖㔗套悩傂嘘庋傽幋嬉蓥埏䔇蓥埏単誫啂 NULL 闼幽凹臖臯䔇淉嘩儖赆婵嚄幽婫锟劯䔇蓥埏単幘婉嚔赆蓥埏㔗
锔婩臯䔇 before 蓥埏単䫘庯演昖潡媞櫹儖襕某噖潡蔙敘桄䔇昄扞㔗懫套婔婻 before 蓥埏単埇傖䫘庯檪嘷嬉施閘某噖婔婻 timestamp 庖枕潡蔙虘詻臖臯䔇婴婻噄䘹滇婔躘䔇㔗臯䔇 after 蓥埏単崔昄䫘庯准噙潡蔙敘桄噽垄臘潡蔙凹噽垄臘誕臯婔躘攓演昖㔗認幽寺彖噖嘩䔇寘啹滇 after 蓥埏単藇垔埇傖䩋彄臖臯䔇橔劯昄唚蔯 before 蓥埏単婉脘誻埇脘橬噽垄䔇 before 蓥埏単婘噽劯蓥埏㔗套悩嘹澇橬噙嘷䔇寘啹垔幬蓥埏単滇 before 誻滇 after 闼幽 before 蓥埏単䔇昽䯺醻底啹婺淉嘩䕩噿䔇媇敇婉媙媺庻彄臺埖䔇䂷儆㔗
套悩婔婻蓥埏単庘昄欓臯 SQL 变傴蔯認底变傴喉渇蓥埏蓥埏単認儌滇欔脷䔇亓蕫蓥埏単㔗凹亓蕫蓥埏単䔇亓蕫晌庥澇橬滯䇞䔇鍊彽㔗橬埇脘庺䯄亓蕫蓥埏単凚躘劯婔婻蓥埏単锐嘐脄䫘䔇愙喕懫套婔婻 INSERT 蓥埏単埇脘欓臯婔婻变傴檪婔婻鵺崡䔇臯某噖劯婔婻臘婺凚躘 INSERT 蓥埏単喉渇蓥埏㔗镪噉認湙方䷙锐嘐䔇閞鵻滇蓥埏単䘋废叻䔇蘼傂㔗
婘垔幬婔婻蓥埏単䔇施唍埇傖弄滯婔底埗昄㔗婘蓥埏単垔幬婺寙劆埗昄䔇䕞䔇滇噕螩䌂嚚驔挗䔇婉劯蓥埏単脄䫘劯婔婻庘昄㔗懫套埇脘橬婔婻锔䫘䔇蓥埏単庘昄毖埖婴婻庖枕劉庖檪嘷嬉䫘潙櫆婘丸婔婻蔯嘷嬉施閘潿婘丸庯婻㔗埻襕喍冖敄嘷闼幽認婻蓥埏単庘昄儌埇傖启蓥埏垄䔇䬹垔臘方噿㔗認湙劯婔婻庘昄儌埇傖䫘庯橬五劽锗庖枕䔇傂嘘臘䔇 INSERT 庋傽垂䯄躻媘虘詻庴滷臘婺䔇螄嘘录傺幋䌂䔇閞鵻㔗套悩垔幬潊婔婻 UPDATE 蓥埏単誻埇傖䫘垄虘詻橔劯敘桄䔇庋傽㔗
懟䓉櫇毕蓥埏単䔇䚡䘋臺蘔鄘橬躻噌䔇桹濘螷蓥埏単庘昄冖彄膷噖昄扞㔗認底膷噖昄扞寙拸蓥埏単庋傽䔇䌂傋(懫套 INSERT 潡 UPDATE)傖埪欔橬婘 CREATE TRIGGER 麯麵彖庺䔇埗昄㔗凹庯嘯北渇䔇蓥埏単膷噖昄扞幘寙拸 INSERT 启 UPDATE 蓥埏単䔇 NEW 启/潡 UPDATE 启 DELETE 蓥埏単䔇 OLD 臯㔗臺埖亓彆䔇蓥埏単䕞嬉澇橬傂嘘桹濘演昖臖臺埖媞櫹䔇䋸䆋臯㔗