大约有 47,000 项符合查询结果(耗时:0.0399秒) [XML]

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Can I apply the required attribute to fields in HTML5?

How can I check if a user has selected something from a <select> field in HTML5? 13 Answers ...
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Counting null and non-null values in a single query

...le and SQL Server (you might be able to get it to work on another RDBMS): select sum(case when a is null then 1 else 0 end) count_nulls , count(a) count_not_nulls from us; Or: select count(*) - count(a), count(a) from us; ...
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Find rows that have the same value on a column in MySQL

...sses and how many times they're used, with the most used addresses first. SELECT email, count(*) AS c FROM TABLE GROUP BY email HAVING c > 1 ORDER BY c DESC If you want the full rows: select * from table where email in ( select email from table group by email having count(*) &g...
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React JSX: selecting “selected” on selected option

In a React component for a <select> menu, I need to set the selected attribute on the option that reflects the application state. ...
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Create a temporary table in a SELECT statement without a separate CREATE TABLE

Is it possible to create a temporary (session only) table from a select statement without using a create table statement and specifying each column type? I know derived tables are capable of this, but those are super-temporary (statement-only) and I want to re-use. ...
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SQL Server loop - how do I loop through a set of records

how do I loop through a set of records from a select? 8 Answers 8 ...
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How do I query if a database schema exists

... Are you looking for sys.schemas? IF NOT EXISTS (SELECT * FROM sys.schemas WHERE name = 'jim') BEGIN EXEC('CREATE SCHEMA jim') END Note that the CREATE SCHEMA must be run in its own batch (per the answer below) ...
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How to deal with SQL column names that look like SQL keywords?

...ange the name because I didn't make it. Am I allowed to do something like SELECT from FROM TableName or is there a special syntax to avoid the SQL Server being confused? ...
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Select data from date range between two dates

...uch more simple (only two cases against four). Your SQL will look like: SELECT * FROM Product_sales WHERE NOT (From_date > @RangeTill OR To_date < @RangeFrom) share | improve this answer ...
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SQL - using alias in Group By

... following order: FROM clause WHERE clause GROUP BY clause HAVING clause SELECT clause ORDER BY clause For most relational database systems, this order explains which names (columns or aliases) are valid because they must have been introduced in a previous step. So in Oracle and SQL Server, you...