我需要检查（来自同一张表）两个事件之间是否存在基于日期时间的关联。
一组数据将包含某些事件的结束日期时间，另一组数据将包含其他事件的开始日期时间。
如果第一个事件在第二个事件之前完成，那么我想将它们链接起来。
到目前为止我所拥有的是：
SELECT name as name_A, date-time as end_DTS, id as id_A
FROM tableA WHERE criteria = 1
SELECT name as name_B, date-time as start_DTS, id as id_B
FROM tableA WHERE criteria = 2
然后我加入他们：
SELECT name_A, name_B, id_A, id_B,
if(start_DTS > end_DTS,'VALID','') as validation_check
FROM tableA
LEFT JOIN tableB ON name_A = name_B
然后我可以根据validation_check字段运行带有SELECT嵌套的UPDATE查询吗？
答案 0 :(得分：712)
您实际上可以采用以下两种方式之一：
MySQL更新连接语法：
UPDATE tableA a
INNER JOIN tableB b ON a.name_a = b.name_b
SET validation_check = if(start_dts > end_dts, 'VALID', '')
-- where clause can go here
ANSI SQL语法：
UPDATE tableA SET validation_check =
(SELECT if(start_DTS > end_DTS, 'VALID', '') AS validation_check
FROM tableA
INNER JOIN tableB ON name_A = name_B
WHERE id_A = tableA.id_A)
选择对你来说最自然的一个。
答案 1 :(得分：264)
UPDATE
`table1` AS `dest`,
(
SELECT
*
FROM
`table2`
WHERE
`id` = x
) AS `src`
SET
`dest`.`col1` = `src`.`col1`
WHERE
`dest`.`id` = x
;
希望这适合你。
答案 2 :(得分：94)
在MySQL中很容易：
UPDATE users AS U1, users AS U2
SET U1.name_one = U2.name_colX
WHERE U2.user_id = U1.user_id
答案 3 :(得分：49)
如果有人试图将数据从一个数据库更新到另一个数据库，无论他们瞄准哪个表，都必须有一些标准来执行此操作。
对于所有级别，这个更好更干净：
UPDATE dbname1.content targetTable
LEFT JOIN dbname2.someothertable sourceTable ON
targetTable.compare_field= sourceTable.compare_field
SET
targetTable.col1 = sourceTable.cola,
targetTable.col2 = sourceTable.colb,
targetTable.col3 = sourceTable.colc,
targetTable.col4 = sourceTable.cold
Traaa！它很棒！
根据上述理解，您可以修改设置字段和“开启”条件来完成工作。您还可以执行检查，然后将数据拉入临时表，然后使用上述语法替换表和列名来运行更新。
希望它有效，如果不让我知道。我会为你写一个确切的查询。
答案 4 :(得分：13)
UPDATE
receipt_invoices dest,
(
SELECT
`receipt_id`,
CAST((net * 100) / 112 AS DECIMAL (11, 2)) witoutvat
FROM
receipt
WHERE CAST((net * 100) / 112 AS DECIMAL (11, 2)) != total
AND vat_percentage = 12
) src
SET
dest.price = src.witoutvat,
dest.amount = src.witoutvat
WHERE col_tobefixed = 1
AND dest.`receipt_id` = src.receipt_id ;
希望在您必须在两个表之间进行匹配和更新的情况下，这将对您有所帮助。
答案 5 :(得分：11)
我在寻找一个非常复杂的连接的自己的解决方案时发现了这个问题。这是一个替代解决方案，对于更复杂的问题版本，我认为这可能是有用的。
我需要在活动表中填充product_id字段，其中活动以单位编号，单位在一个级别编号（使用字符串?? N标识），以便可以使用SKU识别活动，即L1U1A1。然后将这些SKU存储在不同的表中。
我确定了以下内容以获取activity_id与product_id的列表： -
SELECT a.activity_id, w.product_id
FROM activities a
JOIN units USING(unit_id)
JOIN product_types USING(product_type_id)
JOIN web_products w
ON sku=CONCAT('L',SUBSTR(product_type_code,3), 'U',unit_index, 'A',activity_index)
我发现这太复杂了，无法合并到mysql中的SELECT中，所以我创建了一个临时表，并将其与update语句结合使用： -
CREATE TEMPORARY TABLE activity_product_ids AS (<the above select statement>);
UPDATE activities a
JOIN activity_product_ids b
ON a.activity_id=b.activity_id
SET a.product_id=b.product_id;
我希望有人发现这个有用的
答案 6 :(得分：6)
private void copyAssets() {
AssetManager assetManager = mContext.getAssets();
InputStream in = null;
OutputStream out = null;
try {
in = assetManager.open("database_copy.db");
String currentDBPath = "/data/data/com.example.somepackagename/databases/books-db";
out = new FileOutputStream(currentDBPath);
copyFile(in, out);
in.close();
out.flush();
out.close();
} catch(IOException e) {
Log.e("tag", "Failed to copy asset file " , e);
}
}
private void copyFile(InputStream in, OutputStream out) throws IOException {
byte[] buffer = new byte[1024];
int read;
while((read = in.read(buffer)) != -1){
out.write(buffer, 0, read);
}
}
答案 7 :(得分：4)
您可以使用内部联接更新其他表中的值，如此
UPDATE [table1_name] AS t1 INNER JOIN [table2_name] AS t2 ON t1.column1_name] = t2.[column1_name] SET t1.[column2_name] = t2.column2_name];
按照此处了解如何使用此查询http://www.voidtricks.com/mysql-inner-join-update/
或者您可以使用select as子查询来执行此操作
UPDATE [table_name] SET [column_name] = (SELECT [column_name] FROM [table_name] WHERE [column_name] = [value]) WHERE [column_name] = [value];
答案 8 :(得分：3)
您可以使用：
UPDATE Station AS st1, StationOld AS st2
SET st1.already_used = 1
WHERE st1.code = st2.code
答案 9 :(得分：3)
对于同一张桌子，
UPDATE PHA_BILL_SEGMENT AS PHA,
(SELECT BILL_ID, COUNT(REGISTRATION_NUMBER) AS REG
FROM PHA_BILL_SEGMENT
GROUP BY REGISTRATION_NUMBER, BILL_DATE, BILL_AMOUNT
HAVING REG > 1) T
SET PHA.BILL_DATE = PHA.BILL_DATE + 2
WHERE PHA.BILL_ID = T.BILL_ID;
答案 10 :(得分：1)
检查以下查询。
更新表A A A.name_a上的内部联接表B B = B.name_b 设置validation_check = if（start_dts> end_dts，'VALID'，''）
答案 11 :(得分：0)
如果您要从复杂查询进行更新。最好的办法是从查询创建临时表，然后使用临时表作为一个查询更新。
DROP TABLE IF EXISTS cash_sales_sums;
CREATE TEMPORARY TABLE cash_sales_sums as
SELECT tbl_cash_sales_documents.batch_key, COUNT(DISTINCT tbl_cash_sales_documents.cash_sale_number) no_of_docs,
SUM(tbl_cash_sales_documents.paid_amount) paid_amount, SUM(A.amount - tbl_cash_sales_documents.bonus_amount - tbl_cash_sales_documents.discount_given) amount,
SUM(A.recs) no_of_entries FROM
tbl_cash_sales_documents
RIGHT JOIN(
SELECT
SUM(
tbl_cash_sales_transactions.amount
)amount,
tbl_cash_sales_transactions.cash_sale_document_id,
COUNT(transaction_id)recs
FROM
tbl_cash_sales_transactions
GROUP BY
tbl_cash_sales_transactions.cash_sale_document_id
)A ON A.cash_sale_document_id = tbl_cash_sales_documents.cash_sale_id
GROUP BY
tbl_cash_sales_documents.batch_key
ORDER BY batch_key;
UPDATE tbl_cash_sales_batches SET control_totals = (SELECT amount FROM cash_sales_sums WHERE cash_sales_sums.batch_key = tbl_cash_sales_batches.batch_key LIMIT 1),
expected_number_of_documents = (SELECT no_of_docs FROM cash_sales_sums WHERE cash_sales_sums.batch_key = tbl_cash_sales_batches.batch_key),
computer_number_of_documents = expected_number_of_documents, computer_total_amount = control_totals
WHERE batch_key IN (SELECT batch_key FROM cash_sales_sums);