Rumah > Artikel > pangkalan data > Bagaimana untuk menyahduplikasi data dalam oracle
Kaedah penyahduplikasian: 1. Gunakan kata kunci yang berbeza untuk menyahduplikasi, sintakskan "PILIH nama medan DISTINCT DARI nama jadual;" 2. Gunakan fungsi tetingkap row_number () over() untuk menyahduplikasi; klausa untuk menyahduplikasi, sintaksnya ialah "pilih nama medan daripada kumpulan nama jadual mengikut nama medan;" 4. Gunakan rowid untuk menyahduplikasi lajur pseudo.
Persekitaran pengendalian tutorial ini: sistem Windows 7, versi Oracle 11g, komputer Dell G3.
Senario Perniagaan
Perlu menanyakan data tertentu Memandangkan tiga jadual diperlukan untuk pertanyaan berkaitan, hasil pertanyaan adalah seperti berikut:
Pernyataan SQL asal
SELECT D.ORDER_NUM AS "申请单号" , D.CREATE_TIME , D.EMP_NAME AS "申请人", (SELECT extractvalue(t1.row_data,'/root/row/FI13_wasteName') FROM dat_table_row t1 WHERE d.document_id = t1.document_id AND t1.table_id = 'dynamicRowsIdPTFLXX' ) AS "废料名称", (SELECT extractvalue(t1.row_data,'/root/row/FI13_units') FROM dat_table_row t1 WHERE d.document_id = t1.document_id AND t1.table_id = 'dynamicRowsIdPTFLXX' ) AS "单位", (SELECT extractvalue(t1.row_data,'/root/row/FI13_estimate') FROM dat_table_row t1 WHERE d.document_id = t1.document_id AND t1.table_id = 'dynamicRowsIdPTFLXX' ) AS "预估数量", (SELECT extractvalue(t1.row_data,'/root/row/FI13_stockRemoval') FROM dat_table_row t1 WHERE d.document_id = t1.document_id AND t1.table_id = 'dynamicRowsIdPTFLXX' ) AS "累计出库数量", (SELECT extractvalue(t1.row_data,'/root/row/FI13_receivingTime') FROM dat_table_row t1 WHERE d.document_id = t1.document_id AND t1.table_id = 'dynamicRowsIdCGYTX' ) AS "收购方收货时间", (SELECT extractvalue(t2.row_data,'/root/row/FI13_collectionTime') FROM dat_table_row t2 WHERE d.document_id = t2.document_id AND t2.table_id = 'dynamicRowsIdPTSJSKSJ' ) AS "实际收款时间" FROM dat_document d, dat_table_row dtr WHERE d.form_name ='FI14' AND d.document_id =dtr.document_id AND (D.DOCUMENT_STATUS != 'deleted' OR D.DOCUMENT_STATUS IS NULL ) --AND TO_CHAR(d.create_time,'yyyy-MM-dd') BETWEEN '2020-01-01' AND '2021-03-26' AND d.order_num = 'FI1420210708002' --FI1420210708002 ORDER BY d.CREATE_TIME DESC;
Kaedah 1: penyahduplikasi yang berbeza
PILIH DISTINCT boleh digunakan untuk menapis baris Pendua dalam set hasil, pastikan nilai dalam lajur atau lajur yang ditentukan dikembalikan dalam klausa SELECT adalah unik. Sintaks pernyataan DISTINCT adalah seperti berikut:SELECT DISTINCT column_1, column_2, ... FROM table_name;Contoh:
SELECT D.ORDER_NUM AS "申请单号" , D.CREATE_TIME , D.EMP_NAME AS "申请人", (SELECT extractvalue(t1.row_data,'/root/row/FI13_wasteName') FROM dat_table_row t1 WHERE d.document_id = t1.document_id AND t1.table_id = 'dynamicRowsIdPTFLXX' ) AS "废料名称", (SELECT extractvalue(t1.row_data,'/root/row/FI13_units') FROM dat_table_row t1 WHERE d.document_id = t1.document_id AND t1.table_id = 'dynamicRowsIdPTFLXX' ) AS "单位", (SELECT extractvalue(t1.row_data,'/root/row/FI13_estimate') FROM dat_table_row t1 WHERE d.document_id = t1.document_id AND t1.table_id = 'dynamicRowsIdPTFLXX' ) AS "预估数量", (SELECT extractvalue(t1.row_data,'/root/row/FI13_stockRemoval') FROM dat_table_row t1 WHERE d.document_id = t1.document_id AND t1.table_id = 'dynamicRowsIdPTFLXX' ) AS "累计出库数量", (SELECT extractvalue(t1.row_data,'/root/row/FI13_receivingTime') FROM dat_table_row t1 WHERE d.document_id = t1.document_id AND t1.table_id = 'dynamicRowsIdCGYTX' ) AS "收购方收货时间", (SELECT extractvalue(t2.row_data,'/root/row/FI13_collectionTime') FROM dat_table_row t2 WHERE d.document_id = t2.document_id AND t2.table_id = 'dynamicRowsIdPTSJSKSJ' ) AS "实际收款时间" FROM dat_document d, dat_table_row dtr WHERE d.form_name ='FI14' AND d.document_id =dtr.document_id AND (D.DOCUMENT_STATUS != 'deleted' OR D.DOCUMENT_STATUS IS NULL ) --AND TO_CHAR(d.create_time,'yyyy-MM-dd') BETWEEN '2020-01-01' AND '2021-03-26' AND d.order_num = 'FI1420210708002' --FI1420210708002 ORDER BY d.CREATE_TIME DESC;Nota: DISTINCT mesti diikuti dengan medan ORDER BY Oracle terlebih dahulu melakukan DISTINCT untuk mengalih keluar pendua , dan kemudian gunakan ORDER BY untuk mengisih. Oleh itu, jika medan yang perlu diisih mengikut ORDER BY tiada dalam medan selepas berbeza, ralat secara semula jadi akan dilemparkan. Mesej ralat adalah seperti berikut: Format tatabahasa
select * from (select A.*, row_number() over(partition by A.name1 order by A.name12 desc) rn from A) where rn = 1Contoh
select * from ( select d.order_num as "申请单号" , d.create_time , d.emp_name as "申请人", (select extractvalue(t1.row_data,'/root/row/FI13_wasteName') from dat_table_row t1 where d.document_id = t1.document_id and t1.table_id = 'dynamicRowsIdPTFLXX' ) as "废料名称", (select extractvalue(t1.row_data,'/root/row/FI13_units') from dat_table_row t1 where d.document_id = t1.document_id and t1.table_id = 'dynamicRowsIdPTFLXX' ) as "单位", (select extractvalue(t1.row_data,'/root/row/FI13_estimate') from dat_table_row t1 where d.document_id = t1.document_id and t1.table_id = 'dynamicRowsIdPTFLXX' ) as "预估数量", (select extractvalue(t1.row_data,'/root/row/FI13_stockRemoval') from dat_table_row t1 where d.document_id = t1.document_id and t1.table_id = 'dynamicRowsIdPTFLXX' ) as "累计出库数量", (select extractvalue(t1.row_data,'/root/row/FI13_receivingTime') from dat_table_row t1 where d.document_id = t1.document_id and t1.table_id = 'dynamicRowsIdCGYTX' ) as "收购方收货时间", (select extractvalue(t2.row_data,'/root/row/FI13_collectionTime') from dat_table_row t2 where d.document_id = t2.document_id and t2.table_id = 'dynamicRowsIdPTSJSKSJ' ) as "实际收款时间", row_number() over(partition by d.order_num order by d.create_time desc) rn from dat_document d, dat_table_row dtr where d.form_name ='FI14' and d.document_id =dtr.document_id and (d.document_status != 'deleted' or d.document_status is null ) --AND TO_CHAR(d.create_time,'yyyy-MM-dd') BETWEEN '2020-01-01' AND '2021-03-26' and d.order_num = 'FI1420210708002' --FI1420210708002 ) where rn = 1;Hasil pertanyaan
Kaedah 3: kumpulan mengikut
select 字段名 from 表名 group by 字段名;
Kaedah 4: Gunakan rowid (penyahduplikasi lajur pseudo)
select id,name,age from test t1 where t1.rowid in (select min(rowid) from test t2 where t1.name=t2.name and t1.age=t2.age);Tutorial yang disyorkan: "
Tutorial Oracle"
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