I'm trying to retrieve only the data that are not NULL in a database table, but the IS NOT NULL clause does not seem to work. The null fields are also displayed. String sql = "SELECT _id, nome_sotto FROM Categorie WHERE nome_categoria = '"+i.getStringExtra("categoria")+"' AND ...
select n_ajbh,n_sfyyy from t_ywpz_gakh_fkjl where d_fkrq is not null and n_dqyx=1 and n_sfyyy=1 order by n_ajbh) union all select * from ( select n_ajbh,n_sfyyy from t_ywpz_gakh_fkjl where d_fkrq is not null and n_dqyx=1 and n_sfyyy=3 order by n_ajbh);...
import sqlite3 con = sqlite3.connect("mydb")cur = con.cursor()who = "Yeltsin"age = 72 cur.execute("select name_last, age from people where name_last=? and age=?", (who, age))print cur.fetchone()下面的例子展示了如何使用命名：import sqlite3 ...
sqlite> SELECT ID, NAME, AGE, ADDRESS, SALARY FROM COMPANY WHERE SALARY IS NOT NULL; 上面的 SQLite 语句将产生下面的结果: ID NAME AGE ADDRESS SALARY --- --- --- --- --- 1 Paul 32 California 20000.0 2 Allen 25 Texas 15000.0 3 Teddy 23 Norway 20000.0 4 Mark 25 Rich-Mond 65000.0 ...
一、基本的SELECT语句 1、查询所有列 2、查询特定的列 3、列的别名 4、去重 5、+号的作用 二、过滤和排序数据 1、过滤 2、between and 3、in 4、is null 5、order by 子句 三、总结 一、基本的SELECT语句 在数据库中,查询语句算是最基础、最重要的一个的东西了,绝对不能小看的一个特殊元素,就如同班...
在SQLite中,可以使用 IS NULL 或IS NOT NULL 来处理 NULL 值。 例如,如果要查询一个列中包含 NULL 值的记录,可以使用 IS NULL: SELECT * FROM table_name WHERE column_name IS NULL; 复制代码 如果想查询一个列中不包含 NULL 值的记录,可以使用 IS NOT NULL: SELECT * FROM table_name WHERE column_...
SELECT*FROMmy_tableLIMIT10OFFSET20; 这条SQL语句将从my_table表中跳过前20条记录,然后获取接下来的10条记录。这样可以实现分页查询,提高查询效率。 四、IO优化 4.1 使用事务 SQLite在每次事务提交时进行一次磁盘同步,将数据写入磁盘。如果没有使用事务,每个数据库操作都会进行一次磁盘同步,这会导致大量的磁盘I/O操...
values(5,null,0);insert into t1 values(6,null,1);insert into t1 values(7,null,null);-- Check to see what CASE does with NULLs in its test expressionsselect a, case when b<>0 then 1 else 0 end from t1;select a+10, case when not b<>0 then 1 else 0 end from t1;select a...
sqlite>SELECT ID,NAME,AGE,ADDRESS,SALARY FROM COMPANY WHERE SALARY IS NOT NULL; 上面的 SQLite 语句将产生下面的结果: ID NAME AGE ADDRESS SALARY---1Paul32California20000.02Allen25Texas15000.03Teddy23Norway20000.04Mark25Rich-Mond65000.05David27Texas85000.0 下面是IS NULL运算符的用法,将列出所有 SALARY 为...
sqlite>SELECT ID,NAME,AGE,ADDRESS,SALARY FROM COMPANY WHERE SALARY IS NOT NULL; 上面的 SQLite 语句将产生下面的结果: ID NAME AGE ADDRESS SALARY --- --- --- --- --- 1 Paul 32 California 20000.0 2 Allen 25 Texas 15000.0 3 Teddy 23 Norway 20000.0 ...