Sql 查询返回值为0
我试图在SQLDeveloper中执行以下PL/SQL脚本。循环应该返回null的计数,但每次都返回0。 将服务器输出设置为onSql 查询返回值为0,sql,oracle,oracle10g,oracle11g,Sql,Oracle,Oracle10g,Oracle11g,我试图在SQLDeveloper中执行以下PL/SQL脚本。循环应该返回null的计数,但每次都返回0。 将服务器输出设置为on DECLARE --v_count number; v_count_null number; BEGIN execute immediate 'select count(*) from SP_MOSAIX' into v_count; FOR i in (select column_name from all_tab_COLUMNS where table_n
DECLARE
--v_count number;
v_count_null number;
BEGIN
execute immediate 'select count(*) from SP_MOSAIX' into v_count;
FOR i in (select column_name from all_tab_COLUMNS where table_name = 'SP_MOSAIX')
LOOP
select count(*) into v_count_null from SP_MOSAIX where i.column_name IS NULL ;
dbms_output.put_line(v_count_null);
END LOOP;
END;
因此,当我运行此程序时,我得到以下输出:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
但是,如果我手动执行查询替代列名,我会得到结果
select count(*) into v_count_null from SP_MOSAIX where i.column_name IS NULL;
有人能帮忙吗?这里有几件事你需要注意。首先,正如您所提到的,您的COUNT查询是使用i.column\u name的值执行的,该值从不为NULL 其次,
COUNT(*)
返回与WHERE
子句条件匹配的行数,而不考虑NULL
值。如果要计算特定列中有多少notnull
值,则必须明确计算该列中的count
值
请参见以下示例():
Oracle 11g R2架构设置:
CREATE TABLE null_col_vals (
col_without_nulls INTEGER NOT NULL
, col_with_nulls INTEGER
, col_with_mix INTEGER
)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, NULL)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, 1)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, NULL)
/
SELECT
COUNT(col_without_nulls) col_without_nulls
, COUNT(col_with_nulls) col_with_nulls
, COUNT(col_with_mix) col_with_mix
, COUNT(*) all_rows
FROM null_col_vals
| COL_WITHOUT_NULLS | COL_WITH_NULLS | COL_WITH_MIX | ALL_ROWS |
----------------------------------------------------------------
| 3 | 0 | 1 | 3 |
DECLARE
l_count INTEGER;
BEGIN
FOR r_col IN (
SELECT *
FROM all_tab_columns atc
WHERE atc.table_name = 'NULL_COL_VALS'
)
LOOP
dbms_output.put_line(r_col.column_name);
EXECUTE IMMEDIATE 'SELECT COUNT(' || r_col.column_name || ') FROM null_col_vals'
INTO l_count;
dbms_output.put_line(l_count);
END LOOP;
END;
查询1:
CREATE TABLE null_col_vals (
col_without_nulls INTEGER NOT NULL
, col_with_nulls INTEGER
, col_with_mix INTEGER
)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, NULL)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, 1)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, NULL)
/
SELECT
COUNT(col_without_nulls) col_without_nulls
, COUNT(col_with_nulls) col_with_nulls
, COUNT(col_with_mix) col_with_mix
, COUNT(*) all_rows
FROM null_col_vals
| COL_WITHOUT_NULLS | COL_WITH_NULLS | COL_WITH_MIX | ALL_ROWS |
----------------------------------------------------------------
| 3 | 0 | 1 | 3 |
DECLARE
l_count INTEGER;
BEGIN
FOR r_col IN (
SELECT *
FROM all_tab_columns atc
WHERE atc.table_name = 'NULL_COL_VALS'
)
LOOP
dbms_output.put_line(r_col.column_name);
EXECUTE IMMEDIATE 'SELECT COUNT(' || r_col.column_name || ') FROM null_col_vals'
INTO l_count;
dbms_output.put_line(l_count);
END LOOP;
END;
结果:
CREATE TABLE null_col_vals (
col_without_nulls INTEGER NOT NULL
, col_with_nulls INTEGER
, col_with_mix INTEGER
)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, NULL)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, 1)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, NULL)
/
SELECT
COUNT(col_without_nulls) col_without_nulls
, COUNT(col_with_nulls) col_with_nulls
, COUNT(col_with_mix) col_with_mix
, COUNT(*) all_rows
FROM null_col_vals
| COL_WITHOUT_NULLS | COL_WITH_NULLS | COL_WITH_MIX | ALL_ROWS |
----------------------------------------------------------------
| 3 | 0 | 1 | 3 |
DECLARE
l_count INTEGER;
BEGIN
FOR r_col IN (
SELECT *
FROM all_tab_columns atc
WHERE atc.table_name = 'NULL_COL_VALS'
)
LOOP
dbms_output.put_line(r_col.column_name);
EXECUTE IMMEDIATE 'SELECT COUNT(' || r_col.column_name || ') FROM null_col_vals'
INTO l_count;
dbms_output.put_line(l_count);
END LOOP;
END;
如您所见,COUNT(*)
始终返回存在的行数,但其他行数的结果不同,具体取决于指定列中是否存在NULL
值
您需要使用executeimmediate
将列名转换为查询的一部分。类似这样的东西可能会起作用:
查询2:
CREATE TABLE null_col_vals (
col_without_nulls INTEGER NOT NULL
, col_with_nulls INTEGER
, col_with_mix INTEGER
)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, NULL)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, 1)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, NULL)
/
SELECT
COUNT(col_without_nulls) col_without_nulls
, COUNT(col_with_nulls) col_with_nulls
, COUNT(col_with_mix) col_with_mix
, COUNT(*) all_rows
FROM null_col_vals
| COL_WITHOUT_NULLS | COL_WITH_NULLS | COL_WITH_MIX | ALL_ROWS |
----------------------------------------------------------------
| 3 | 0 | 1 | 3 |
DECLARE
l_count INTEGER;
BEGIN
FOR r_col IN (
SELECT *
FROM all_tab_columns atc
WHERE atc.table_name = 'NULL_COL_VALS'
)
LOOP
dbms_output.put_line(r_col.column_name);
EXECUTE IMMEDIATE 'SELECT COUNT(' || r_col.column_name || ') FROM null_col_vals'
INTO l_count;
dbms_output.put_line(l_count);
END LOOP;
END;
这里有几件事你需要注意。首先,正如您所提到的,您的COUNT查询是使用i.column\u name的值执行的,该值从不为NULL 其次,
COUNT(*)
返回与WHERE
子句条件匹配的行数,而不考虑NULL
值。如果要计算特定列中有多少notnull
值,则必须明确计算该列中的count
值
请参见以下示例():
Oracle 11g R2架构设置:
CREATE TABLE null_col_vals (
col_without_nulls INTEGER NOT NULL
, col_with_nulls INTEGER
, col_with_mix INTEGER
)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, NULL)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, 1)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, NULL)
/
SELECT
COUNT(col_without_nulls) col_without_nulls
, COUNT(col_with_nulls) col_with_nulls
, COUNT(col_with_mix) col_with_mix
, COUNT(*) all_rows
FROM null_col_vals
| COL_WITHOUT_NULLS | COL_WITH_NULLS | COL_WITH_MIX | ALL_ROWS |
----------------------------------------------------------------
| 3 | 0 | 1 | 3 |
DECLARE
l_count INTEGER;
BEGIN
FOR r_col IN (
SELECT *
FROM all_tab_columns atc
WHERE atc.table_name = 'NULL_COL_VALS'
)
LOOP
dbms_output.put_line(r_col.column_name);
EXECUTE IMMEDIATE 'SELECT COUNT(' || r_col.column_name || ') FROM null_col_vals'
INTO l_count;
dbms_output.put_line(l_count);
END LOOP;
END;
查询1:
CREATE TABLE null_col_vals (
col_without_nulls INTEGER NOT NULL
, col_with_nulls INTEGER
, col_with_mix INTEGER
)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, NULL)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, 1)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, NULL)
/
SELECT
COUNT(col_without_nulls) col_without_nulls
, COUNT(col_with_nulls) col_with_nulls
, COUNT(col_with_mix) col_with_mix
, COUNT(*) all_rows
FROM null_col_vals
| COL_WITHOUT_NULLS | COL_WITH_NULLS | COL_WITH_MIX | ALL_ROWS |
----------------------------------------------------------------
| 3 | 0 | 1 | 3 |
DECLARE
l_count INTEGER;
BEGIN
FOR r_col IN (
SELECT *
FROM all_tab_columns atc
WHERE atc.table_name = 'NULL_COL_VALS'
)
LOOP
dbms_output.put_line(r_col.column_name);
EXECUTE IMMEDIATE 'SELECT COUNT(' || r_col.column_name || ') FROM null_col_vals'
INTO l_count;
dbms_output.put_line(l_count);
END LOOP;
END;
结果:
CREATE TABLE null_col_vals (
col_without_nulls INTEGER NOT NULL
, col_with_nulls INTEGER
, col_with_mix INTEGER
)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, NULL)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, 1)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, NULL)
/
SELECT
COUNT(col_without_nulls) col_without_nulls
, COUNT(col_with_nulls) col_with_nulls
, COUNT(col_with_mix) col_with_mix
, COUNT(*) all_rows
FROM null_col_vals
| COL_WITHOUT_NULLS | COL_WITH_NULLS | COL_WITH_MIX | ALL_ROWS |
----------------------------------------------------------------
| 3 | 0 | 1 | 3 |
DECLARE
l_count INTEGER;
BEGIN
FOR r_col IN (
SELECT *
FROM all_tab_columns atc
WHERE atc.table_name = 'NULL_COL_VALS'
)
LOOP
dbms_output.put_line(r_col.column_name);
EXECUTE IMMEDIATE 'SELECT COUNT(' || r_col.column_name || ') FROM null_col_vals'
INTO l_count;
dbms_output.put_line(l_count);
END LOOP;
END;
如您所见,COUNT(*)
始终返回存在的行数,但其他行数的结果不同,具体取决于指定列中是否存在NULL
值
您需要使用executeimmediate
将列名转换为查询的一部分。类似这样的东西可能会起作用:
查询2:
CREATE TABLE null_col_vals (
col_without_nulls INTEGER NOT NULL
, col_with_nulls INTEGER
, col_with_mix INTEGER
)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, NULL)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, 1)
/
INSERT INTO null_col_vals (col_without_nulls, col_with_nulls, col_with_mix)
VALUES (1, NULL, NULL)
/
SELECT
COUNT(col_without_nulls) col_without_nulls
, COUNT(col_with_nulls) col_with_nulls
, COUNT(col_with_mix) col_with_mix
, COUNT(*) all_rows
FROM null_col_vals
| COL_WITHOUT_NULLS | COL_WITH_NULLS | COL_WITH_MIX | ALL_ROWS |
----------------------------------------------------------------
| 3 | 0 | 1 | 3 |
DECLARE
l_count INTEGER;
BEGIN
FOR r_col IN (
SELECT *
FROM all_tab_columns atc
WHERE atc.table_name = 'NULL_COL_VALS'
)
LOOP
dbms_output.put_line(r_col.column_name);
EXECUTE IMMEDIATE 'SELECT COUNT(' || r_col.column_name || ') FROM null_col_vals'
INTO l_count;
dbms_output.put_line(l_count);
END LOOP;
END;
您需要使用动态SQL,这将允许您引用每一列:
FOR i in (select column_name from all_tab_COLUMNS where table_name = 'SP_MOSAIX')
LOOP
execute immediate 'select count(*) from SP_MOSAIX where '||i.column_name||' IS NULL'
into v_count_null ;
dbms_output.put_line(i.column_name||' = '||v_count_null);
END LOOP;
您需要使用动态SQL,这将允许您引用每一列:
FOR i in (select column_name from all_tab_COLUMNS where table_name = 'SP_MOSAIX')
LOOP
execute immediate 'select count(*) from SP_MOSAIX where '||i.column_name||' IS NULL'
into v_count_null ;
dbms_output.put_line(i.column_name||' = '||v_count_null);
END LOOP;
它返回0,因为i.column\u name被视为变量,而不是列。现在的问题是如何将其设置为实际列vaule而不是VARIABLE在第二个select语句中,表SP_MOSAIX没有别名“i”。请参阅SQL别名:它返回0,因为i.column\u name被视为变量而不是列。现在的问题是如何将其设置为实际列vaule而不是VARIABLE在第二个select语句中,表SP_MOSAIX没有别名“i”。请参阅SQL别名:感谢您的精彩解释和帮助。。。我的问题解决了。。。谢谢你精彩的解释和帮助。。。我的问题解决了。。。thnx。。