database

问题 I am getting an error after moving the project to production. The error is as follows while running with production server pg_connect(): Unable to connect to PostgreSQL server: SCRAM authentication requires libpq version 10 or above. Here is my postgreSQL version: Development Version : PostgreSQL 11.5 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-36), 64-bit Production Version : PostgreSQL 11.5 (EnterpriseDB Advanced Server 11.5.12) on x86_64-pc-linux-gnu,

问题 I am getting an error after moving the project to production. The error is as follows while running with production server pg_connect(): Unable to connect to PostgreSQL server: SCRAM authentication requires libpq version 10 or above. Here is my postgreSQL version: Development Version : PostgreSQL 11.5 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-36), 64-bit Production Version : PostgreSQL 11.5 (EnterpriseDB Advanced Server 11.5.12) on x86_64-pc-linux-gnu,

问题 I have a field in my Mysql table whose values are ('Yes','No') which is enum data type. Here I want to set its default value as 'No'. But when I am setting it as 'No', it takes no value. How will I do this? 回答1: CREATE TABLE enum_test ( enum_fld ENUM('Yes', 'No') DEFAULT 'No' ); or something like this 回答2: If an ENUM column is declared to permit NULL , the NULL value is a legal value for the column, and the default value is NULL . If an ENUM column is declared NOT NULL , its default value is

问题 I have a field in my Mysql table whose values are ('Yes','No') which is enum data type. Here I want to set its default value as 'No'. But when I am setting it as 'No', it takes no value. How will I do this? 回答1: CREATE TABLE enum_test ( enum_fld ENUM('Yes', 'No') DEFAULT 'No' ); or something like this 回答2: If an ENUM column is declared to permit NULL , the NULL value is a legal value for the column, and the default value is NULL . If an ENUM column is declared NOT NULL , its default value is

问题 Is there any significance in the order of table in sql join statement. For example SELECT dept_name, emp_name FROM Employee INNER JOIN Department ON Employee.dept_id = Department.dept_id and SELECT dept_name, emp_name FROM Department INNER JOIN Employee ON Employee.dept_id = Department.dept_id Is there is any performance advantage in the order of tables? 回答1: No there isn't. Most (if not all) DBMS's use of a Cost based optimizer. The order in which you specify your statements does not affect

问题 I want to know if it is possible to use Spring Batch , in order to read from an file Excel and save it in Database. remark : the content of file Excel chang every 2 hours. And if it is not possible with Spring Batch, what other solution can i use 回答1: Go take a look on spring-batch-extensions for Excel. You will find some examples of ExcelItemReader and ExcelItemWriter. Here is the introduction of the spring-batch-extensions project for Excel : Spring Batch extension which contains ItemReader

问题 Closed . This question needs details or clarity. It is not currently accepting answers. Want to improve this question? Add details and clarify the problem by editing this post. Closed 7 years ago . Improve this question In my Asp.NET MVC4 application I want to add a field to my model without adding it to the database. Sort of a field that only lives in c# instances of the model but not in the database itself. Is there any annotation or other way to exclude the field from the database itself?

问题 This has to be easy, but i can't seem to figure it out... Let say i had a collection users and this is the first item in the collection: { "_id" : ObjectId("4d8653c027d02a6437bc89ca"), "name" : "Oscar Godson", "email" : "oscargodson@xxx.com", "password" : "xxxxxx", "tasks" : [ { "task" : "pick up stuff", "comment" : "the one stuff over there" }, { "task" : "do more stuff", "comment" : "lots and lots of stuff" } ] } How with the PHP driver for MongoDB would I then go and add another "task" to

问题 This has to be easy, but i can't seem to figure it out... Let say i had a collection users and this is the first item in the collection: { "_id" : ObjectId("4d8653c027d02a6437bc89ca"), "name" : "Oscar Godson", "email" : "oscargodson@xxx.com", "password" : "xxxxxx", "tasks" : [ { "task" : "pick up stuff", "comment" : "the one stuff over there" }, { "task" : "do more stuff", "comment" : "lots and lots of stuff" } ] } How with the PHP driver for MongoDB would I then go and add another "task" to

问题 I have changed one of the fields of my collection in mongoDB from an array of strings to an array of object containing 2 strings. New documents get inserted without any problem, but when a get method is called to get , querying all the documents I get this error: Failed to decode 'Students'. Decoding 'photoAddresses' errored with: readStartDocument can only be called when CurrentBSONType is DOCUMENT, not when CurrentBSONType is STRING. photoAddresses is the field that was changed in Students.