SQL queries the total number of qualified records in the database.

SQL queries the total number of qualified records in the database.

1. select count (*) from table; // count the number of tuples

2. select count (column name) from table; // count the number of values in a column

3. select count (*) from table where field = ""; // The total number of records that meet the condition

4. SQL _count = "select count (*) from article a where 1 = 1 ";

// In this statement, a represents the article table. You can write a. field next to it to represent the field of the table. where 1 = 1, which is equivalent to providing a where. Because 1 = 1 is always true.

You can add and a. Field = "" after the statement based on whether or not to add conditions.

Example:

SQL _count = "select count (*) from article a where 1 = 1"; if (! "". Equals (title) & title! = Null) {SQL _count + = "and a. a_title like '%" + title + "% '";}

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