2/19/2023 0 Comments Postgresql cast![]() ![]() ![]() Finally, we used to_timestamp() to convert it back to the original date and time value. We then used extract() to get the Unix timestamp from that date and time value. In this example we used now() to output the current date and time. Result: Current Date/Time | Unix Timestamp | And back again. To_timestamp(extract(epoch from now())) AS "And back again." Here’s another example that further demonstrates how the result reflects the Unix timestamp value provided: SELECTĮxtract(epoch from now()) AS "Unix Timestamp", In this case I passed a specific Unix timestamp value. Here’s a simple example to demonstrate: SELECT to_timestamp(1912995045) The Unix timestamp (also known as Unix Epoch time, Unix time, or POSIX time) is the number of seconds that have elapsed since 00:00:00 Thursday, 1 January 1970, Coordinated Universal Time (UTC). However, in many cases you can compose on top of the query using the Include operator to return related data (see Including related data).In PostgreSQL, we can use the to_timestamp() function to convert a Unix timestamp value to a date/time value. The SQL query can't contain related data.Note that this behavior is different from EF6 EF6 ignored property-to-column mapping for SQL queries, and result set column names had to match those property names. The column names in the result set must match the column names that properties are mapped to.The SQL query must return data for all properties of the entity type.There are a few limitations to be aware of when returning entity types from SQL queries: It's recommended to use those APIs whenever possible, instead of ExecuteSql. Instead, you should use tochar to format the date when you query it, or format it in the client application. EF Core 7.0 introduced ExecuteUpdate and ExecuteDelete, which made it possible to express efficient bulk update operations via LINQ. You can use DateStyle to control how PostgreSQL emits dates, but its global and a bit limited. Prior to EF Core 7.0, it was sometimes necessary to use the ExecuteSql APIs to perform a "bulk update" on the database, as above this is considerably more efficient than querying for all matching rows and then using SaveChanges to modify them. ExecuteSql protects against SQL injection by using safe parameterization, just like FromSql, and ExecuteSqlRaw allows for dynamic construction of SQL queries, just like FromSqlRaw does for queries. This executes the provided SQL and returns the number of rows modified. Var rowsModified = ($"UPDATE SET = NULL") This can be done via ExecuteSql: using (var context = new BloggingContext()) In some scenarios, it may be necessary to execute SQL which does not return any data, typically for modifying data in the database or calling a stored procedure which doesn't return any result sets. SqlQueryRaw allows for dynamic construction of SQL queries, just like FromSqlRaw does for entity types. If you'd like to use a type not supported by your database provider, you can use pre-convention configuration to define a value conversion for it. Where(id => id > (b => b.BlogId))įromSql can be used with any scalar type supported by your database provider. For example, the following query returns the IDs which are above the ID average: var overAverageIds = context.Database However, since your SQL becomes a subquery whose output column needs to be referenced by the SQL EF adds, you must name the output column Value. You can also compose LINQ operators over your SQL query. For example, the following query fetches all the IDs from the Blogs table: var ids = context.Database While FromSql is useful for querying entities defined in your model, SqlQuery allows you to easily query for scalar, non-entity types via SQL, without needing to drop down to lower-level data access APIs. This feature was introduced in EF Core 7.0. FromSql($"EXECUTE dbo.GetMostPopularBlogsForUser )") The following example passes a single parameter to a stored procedure by including a parameter placeholder in the SQL query string and providing an additional argument: var user = "johndoe" However, the FromSqlRaw method can be vulnerable to SQL injection attacks, if improperly used. The FromSql and FromSqlInterpolated methods are safe against SQL injection, and always integrate parameter data as a separate SQL parameter. To learn more about SQL injection, see this page. SQL injection occurs when a program integrates a user-provided string value into a SQL query, and the user-provided value is crafted to terminate the string and perform another malicious SQL operation. When introducing any user-provided values into a SQL query, care must be taken to avoid SQL injection attacks. Pay close attention to parameterization when using SQL queries ![]()
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